I think he just wanted to stop Congress from putting a limitation in the authorization, because the President never wants to be limited, but the President limited himself by going to Congress and asking for authorization, which he seems also to maintain that he doesn't need:
Later, Kerry returned to the question, saying “I don’t want anyone misinterpreting this from me earlier” and specifying that in the authorization of force proposed by the administration “there’s zero capacity” for ground troops. Kerry reiterated that he was “hypothesizing” about potential future scenarios, “but not in this authorization.”Why is he using the word "authorization"? Shouldn't the secret argument be that if they suddenly need to react to a fluid situation by putting boots on the ground, the President has the power to do that, just as the President believes he can launch the air attack on his own, but is simply choosing to ask Congress to approve? What he doesn't want — I would think — is for this approval to contain any disapproval.
The President is strongest when he acts in accordance with Congress's expressed approval. The middle level of power is acting alone, where Congress is silent. He's got the least power when he's acting against the position taken by Congress. He doesn't want his effort to get into category 1 with respect to the air attack to deprive him of the category 2 level of power with respect to other actions he might want to take in the future. He doesn't want to get stuck in category 3.