First, let me say it's not two different opinions. It's about science and facts. If you ignore the CYA your pool isn't disinfected properly. That's what happens. There are some pool stores that have people that have trained themselves. But most do not really have a grasp on the science. Many have no idea about the relationship between CYA and FC that is required. Testing equipment needs to be properly maintained and properly trained personnel. This is very is not always done right. Does this mean all pool stores have bad testing? NO, some days you have somebody that properly cleans, calibrates, and knows the proper procedure and had clean glassware to work with. It does happen. Problem is you don't know if you got a "good test" or not 'till its too late.
If you have questions about how to use TFP or why it works we are happy to answer. But we're not really here to debate. It's up to you to decide if you want to do this and even if you decide not to we'll be here to help any way we can. I hope you decide to give it a try.
Good luck.
Chris