First, here is a current thread on topic:
https://www.disboards.com/threads/flight-of-passage-people-of-size-disappointing.3608328/
Second, it's not an issue of people being asked not to ride, it's a matter of certain body types not being able to be properly restrained. There are a specific set of instructions to get onto the ride and also a test seat to try out before entering the queue. I really don't think this is truly a matter of many people not actually being able to ride, but the thread has many people worried and wondering.