I don't know what charts you're looking at but every supplier of gas chlorinator equipment we've used supplies poly tubing (HDPE) with their kits. The wholesalers all have poly. Worksafe (like OSHA), and the health authorities are all fine with HDPE. Every municipality I've ever talked to that also uses gas uses HDPE save one; they use Kynar at over 10x the price that is still replaced every few years.

Why does the industry use HDPE if it's not the best on the charts? Probably because the more resistant products cost too much when compared to the material and labour required to periodically replace the less resistant products. These systems require frequent changing of tanks to the material must remain flexible and mechanically stable despite the stresses it's subjected to.

That's about all I can tell you. If you wish to consider anyone using poly as unprofessional that's your prerogative.