And this is one of the biggest frustrations, indeed why the poster upset about WDW changing the opening time was so rightfully upset.
Its completely unfair to ask people who often start booking trips a year out, have to book ADRs at 180, FPs at 60 and then be paid in full at 45 ... to then change what you have told them would be available days before the trip, or day of the trip ... etc ?
Launch last minute tests etc (like offering FP only on some attractions) without notice ...
.