I hear ya - 100%. The pool and FG industry has owner's with their hands tied for sure. But to be fair (just a little), as a business they have to provide "some" sort of standardization in the manual, so they use the generic pool industry levels. Without "something" as guidance, you can imagine all the FG owners who really never care for their water at all, then claim a warranty issue one year later. I'm not defending them, but they have to publish some guidance. Unfortunately, they don't recognize some of the very obvious chemical adjustments necessary for certain climates, equipment, or types of chlorination. Would you believe my Viking manual states to test TA every 4-6 weeks, CH every 2-3 months, and CYA every six months? That on top of the ridiculous "recommended levels" they prescribe. Oh, and here's the kicker from the manual .... "Water which is perfectly acceptable for household use may be totally unacceptable for your pool. This is the reason your pool water must be professionally tested and balanced every six to eight weeks." Bwahaahaaaa!
But, TFP care keeps our water crystal clear. We enjoy our FG pool very much, and any cosmetic issues do no take away from our enjoyment each season. Each pool type has its pros & cons, but for us, FG was the choice in-part because it was economical and we have lots of dogs. I could just see the first set of claws digging into a liner, and our soil stinks in this area (moving clay).
The TFP Recommended Levels are proven to be safe and effective for FG. If you have concerns for your warranty, all you have to do is follow your manual requirements for periodic testing. I'm sure that's something you can adjust and have done as needed just in case.