1/ De Blasio confirms what we've known to be true for a while - the 3 percent number was NOT part of a collective bargaining agreement or any one deal with the UFT. This was BdB's call, not Mulgrew's.
But this is how the UFT works:

2/ Mulgrew was obviously exerting constant pressure on City Hall throughout the summer, so BdB felt pressure to create extremely conservative health and safety measures to avoid a strike. Mulgrew likes the 3 percent number, but he didn't come up with it.

3/ Would BdB have settled on 3 percent if he wasn't facing a revolt from the teachers union? Maybe not. But it was decided on as part of a package that the city hoped would calm the union, including ventilation, universal masking, etc.

4/ Also - under de Blasio, the UFT has always had enormous influence over almost every major decision that is made about the NYC public school district. This is the status quo, it didn't happen because of the reopening drama