A new article addressing whether PFAS finishes on upholstery fabric actually work (Spoiler alert - they don't) has been published and can be found here:
https://journals.sagepub.com/doi/10.1177/24723444231159856
This is authored by the fine folks at Green Science Policy, Arlene Blum's group that is the source of the Six Classes of Chemicals
https://greensciencepolicy.org/
https://www.sixclasses.org/
GSP realized that nobody had actually studied whether these very harmful chemicals, that are added ALOT to various fabrics actually do what they claim to do. So they did some research and wrote it up.
Basically:
-water based stains are easier to remove (from both treated and untreated) fabrics. Oil based stains are more difficult.
-newly treated fabric works far better as these treatments do wear off and need to be re-applied. I have heard from other sources yearly is the general idea for re-application.
-Also, these PFAS treatments do block the ability to actually clean the fabric once it is stained.
-The secret appears to be cleaning up stains quickly.
My conclusion: general advice we all got from our Mothers growing up would appear to be of more use than applying PFAS to any fabric.