Since you helped me last night, I'll try to bring some of my scientific training to bear to help you.
If there is one thing you never, ever want to do in science (and I assume medicine is no exception, although it is not my field), it is base knowledge off of one single study. Not all studies are created equal. Some contain more bias than others and it is pretty much impossible to design a 100% unbiased, completely objective experiment. Repeatability is a huge factor, as in can another scientist in another lab using similar techniques procure the same or similar results?
My understanding of BFS is that it's not a very hot area of study because (I'm learning) it's very common and normally completely benign. Funding is often focused on better causes (like figuring out how to better treat/cure ALS).
I'm completely with you man, I'm not totally over my ALS fears yet. I almost laughed when I read this title because I have found so many other seemingly more imminent ALS fears to worry about, that I hadn't even thought of this one yet :). This is the post of someone who has probably done a TON of online research on ALS, who has found ways to reassure the majority of their ALS fears, and who's ALS anxiety is making one final pushback by latching on to the BFS and worrying about it progressing!
I guess the one thing I would rationalize (and believe me, I know how far rationalization goes when you are in panic mode) is that BFS seems to be an extremely common condition with millions of people experiencing it, where as ALS remains rare (the 5,000 new cases every year in a nation of 300,000,000 as well as the 1-4 in 100,000 are one of the few things all sources seem to agree on).
With that said, if anxiety brings on BFS, and BFS were to bring on ALS, than one would expect to see a heck of a lot more diagnoses in a year! Just my thoughts.