Given the way the error is described, it sounds like it would have let him to book if it was after 2pm return time.
But, this definitely messes with the strategy of stacking for your second park. If you're doing HS second, try for slinky at 7, and happen to get assigned a time before 2, it'll error on you. In the meantime, you end up losing any chance at slinky because all the slots are gone when you try again.
The automatic reassign to 2pm for hoppers was one of the few ways this system worked well and now they've broken that, too.