Why waste your time writing this:
It's not just 75% - the first phase is 75% for a full difficulty adjustment period.
When they stay at 75% for a full difficulty adjustment period then they will start broadcasting willingness to mine a bigger block.
When enough have signalled intent to accept bigger blocks for a full adjustment period WITHOUT dropping below 75% then they will start mining bigger blocks.
That's what I have seen them posting, so it will take maintaining 75% consensus for several difficult adjustment periods BEFORE the first bigger blog.
When you could just be honest and admit that this is the real "consensus mechanism" in BU:
The only thing that could throw a wrench in that is UASF in which case they may need to emergency hard fork earlier.
....which is just an invitation to an endless string of noisy, shouty 51% fork after 51% fork?
Alice Wonder, why aren't you able to present clear, honest arguments?