Sorry, Bruce, I'm not buying it. Maybe in warm climes is not good. But in northern, colder climes, PVC will crack all to pieces. Flex is good stuff up here, period.
Another consideration, Bruce is that you mention tie wires and rebars. Thats all a well and good thing to think about. however, realize that most pools built in the northern US and NE are vinyl. Gunnite pools are few and far between. Too many issues with them in cold climates. The applications up here are mainly with vinyl pools where a lot of the pipe is encased in a concrete collar anyway. I know at least 6 vinyl builers in Massachusetts alone that use it with no issue. With frozen ground and frost heaves, flex or poly IS the proper application for vinyl pools built in cold climates.
With all due respect, Bruce, telling people that using flex in ALL cases is of the devil, is, in my opinion, short sighted and shows a biased thats not fair to those who have it or have builders who will use it for the proper applications. Not everyone lives where it doesnt freeze, and own gunnite pools. Again, with all due respect, I'm sure you know your business, but until you have worked in climates where it gets down below zero, where water lines have to be buried 5 feet, and the majority of pools are vinyl construction with no rebar or tie wires, then its hard to understand how construction techniques vary. Just because you dont like it doesnt mean it's bad everywhere. You say yourself you have no knowledge of freezing and frost heaves. Come to
New England in late January and i'll show you.
FWIW, the two "excuses" you cite are actually good reasons, IMO, to use flex.
Just my 2 cents here.