When an article has self contradicting claims I liked to check them out with other sources. If PFA's are truly forever chemicals they should have little to no effect cancer wise on a person And that seems to be the case. This is the first trustworthy article that I found:
PFAS Exposure and Risk of Cancer.
It appears that there may be a tie between people that work at such plants and the surrounding communities, but it is not obvious. One always has to remember that there is often a normal baseline rate for cancers. And unless it is something like smoking it can be hard to definitely blame an effect for only one cause.
Frankly, I am pretty sure that they do detect those chemicals in our rainwater, and I do not want them there myself. But that does not necessarily mean that rainwater is not safe to drink.