Whatever happened to the affirmative action concept of "critical mass"?

From the majority opinion in the new case, Students for Fair Admission v. Harvard:

The principal dissent’s reliance on Fisher II is similarly mistaken. There, by a 4-to-3 vote, the Court upheld a “sui generis” race-based admissions program used by the University of Texas, 579 U. S., at 377, whose “goal” it was to enroll a “critical mass” of certain minority students, Fisher I, 570 U. S., at 297. But neither Harvard nor UNC claims to be using the critical mass concept—indeed, the universities admit they do not even know what it means. See 1 App. in No. 21–707, at 402 (“[N]o one has directed anybody to achieve a critical mass, and I’m not even sure we would know what it is.” (testimony of UNC administrator)); 3 App. in No. 20–1199, at 1137–1138 (similar testimony from Harvard administrator).

But the dissenting opinions never use the term "critical mass."

The only other mention of "critical mass" is in the concurring opinion by Justice Gorsuch:

Following Bakke, this Court declared that judges may simply “defer” to a school’s assertion that “diversity is essential” to its “educational mission.” Grutter, 539 U. S., at 328. Not all schools, though—elementary and secondary schools apparently do not qualify for this deference.... Only colleges and universities, the Court explained, “occupy a special niche in our constitutional tradition.” Grutter, 539 U. S., at 329. Yet even they (wielding their “special niche” authority) cannot simply assert an interest in diversity and discriminate as they please. Fisher, 579 U. S., at 381. Instead, they may consider race only as a “plus” factor for the purpose of “attaining a critical mass of underrepresented minority students” or “a diverse student body.” Grutter, 539 U. S., at 335–336 (internal quotation marks omitted).

So is "critical mass" something no one believes in anymore? Here's how I — as a lawprof teaching these cases — explained it a decade ago:

"Critical mass" was a key phrase in Grutter. The law school explained its interest in classroom diversity in terms of the need to gain a "critical mass" of students who were members of "underrepresented" minority groups. The term was "understood to mean a number that encourages underrepresented minority students to participate in the classroom and not feel isolated... or like spokespersons for their race." One expert had testified that "when a critical mass of underrepresented minority students is present, racial stereotypes lose their force because nonminority students learn there is no '"minority viewpoint"' but rather a variety of viewpoints among minority students."

Interestingly, the "critical mass" that the law school sought had to do with the value of different viewpoints, not the idea that if enough people think one thing then a point will be reached when everyone will tip into thinking the same thing.

Maybe "critical mass" was a transitory concept, useful to appeal to Justices who might oppose affirmative action and who needed a way to connect race with enriching classroom discussions — such as Justice Powell way back in Bakke and, later, Justices O'Connor and Kennedy.

Maybe it's just not useful anymore. The majority of the Court — judging from the main opinion (by Chief Justice Roberts) and the Gorsuch concurrence — says "critical mass" as if it's practically nonsense, and the dissenters avoid it — perhaps because as long as they've lost, they have something else they'd prefer to say about the reason for supporting affirmative action. 

Have the dissenting opinions (by Justices Sotomayor and Jackson) abandoned the idea that racial diversity in the classroom is supposed to benefit everyone by undermining stereotypes and widening the range of viewpoints?

No. They don't say "critical mass," for whatever reason, but the idea is still there.

Here's Justice Sotomayor:

The Court goes as far as to claim that Bakke’s recognition that Black Americans can offer different perspectives than white people amounts to a “stereotype.” Ante, at 29....

The absence of racial diversity... actually contributes to stereotyping. “[D]iminishing the force of such stereotypes is both a crucial part of [respondents’] mission, and one that [they] cannot accomplish with only token numbers of minority students.” Grutter, 539 U. S., at 333. When there is an increase in underrepresented minority students on campus, “racial stereotypes lose their force” because diversity allows students to “learn there is no ‘minority viewpoint’ but l rather a variety of viewpoints among minority students.” Id., at 319–320. By preventing respondents from achieving their diversity objectives, it is the Court’s opinion that facilitates stereotyping on American college campuses.

I think "critical mass" was mostly a way to re-label racial balancing, to let schools just look at the numbers and not need to do the difficult work of judging the applicant as a collection of various attributes. As Sotomayor recognizes, that sort of "holistic" approach remains permissible:

To be clear, today’s decision leaves intact holistic college admissions and recruitment efforts that seek to enroll diverse classes without using racial classifications. Universities should continue to use those tools as best they can to recruit and admit students from different backgrounds based on all the other factors the Court’s opinion does not, and cannot, touch. 

Colleges and universities can continue to consider socioeconomic diversity and to recruit and enroll students who are first-generation college applicants or who speak multiple languages.... At SFFA’s own urging, those efforts remain constitutionally permissible. See Brief for Petitioner 81–86 (emphasizing “race-neutral” alternatives that Harvard and UNC should implement, such as those that focus on socioeconomic and geographic diversity, percentage plans, plans that increase community college transfers, and plans that develop partnerships with disadvantaged high schools)....

CORRECTION: This post originally referred to the Gorsuch opinion as a dissent.