I've noticed all the AEs have that buyer beware message, essentially saying don't bid a seat because you think you'll be withheld, then come complaining to us when we send you to class.

At what point would the company withhold you?
Obvious situations like a 64 year old 73N A with 11 months to go who bids and is awarded A350 A?
Were there situations during COVID where certain A or B seats were short staffed and they weren't letting people leave? Or even today - there are a ton of B717 B slots for newhires....are they letting folks whose seatlocks are up bid out of those seats?
Other situations like base closures and they try to keep a certain amount of staffing to the end.
Anything else? They just emphasize it so much, I suspect in the past it probably happened more often.