What if other people already know about the breach? Would you prefer the joy of ignorance, or would you rather protect yourself by some means?
Microsoft do issue out of band updates but they are very rare and for very serious issues.
It isn't like Microsoft was stalling for time, they didn't ask for months, they asked for days to fir into their scheduled releases. It's also worth pointing out the enterprises time things on the patch Tuesday cycle. An earlier release causes all sorts of implementation problems, especially if only a day or two in advance. In all likelihood you wouldn't see many machines actually updated in that period, but cause significant extra grief.
Yes. Google designed Project Zero to "pressure firms into dealing with security problems more quickly." A firm policy with unambiguous enforcement has its advantages. Muddying the 90-day deadline with questions about when (and for whom) to make exceptions weakens it. For example, in the future, I expect Microsoft will not wait the extra two days in the event of a security disclosure from Google.
One may disagree with the 90-day policy to begin with. I, for one, think it should have had an exception process built in. But while these are Google policies, not laws, I respect them for adhering to published protocol. Even when it was difficult.