I believe the claim being made here is that "a beyond burger" is a thing which fast food chains and supermarkets will offer as an alternative to "a beef burger", that almost nobody will make their own burgers.

I have no opinion about the economics of the brand itself; as a vegetarian I've always thought they were over-priced, and also that it was a shame I don't have a huge range of alternatives, as I actually like spicy bean burgers and can't find them any more*. In fact, because of the limited alternatives in my local markets, I got a kit for making my own burgers from dehydrated soy mince and/or mashed kidney beans.

* I don't know how much of this is "bean burgers are no longer popular" vs. "I moved country and Berlin has never heard of them"; for Quorn I do at least know it's the latter.