So, did "A recent change" now require miscibility that did not exist previously?
Lack of "miscibility " may not in most cases effect actual braking I suspect (even if it did exist) which seems to be the antidotal answer here.
They require purple for a reason in 5 and not 5.1 for a reason, and I suspect it's not for protection of paint.

Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.