> long COVID is probably more accepted as a real thing by practitioners at this point than CFS

Isn't long covid just CFS that can be attributed to Covid?

If you accept that multiple viruses can cause "long <virus>" syndromes, of which long covid is just one example, it's plausible that CFS is really a cluster of syndromes, one category of which is these post viral syndromes. We just can't pinpoint the virus behind it every time because most viruses haven't been studied as much as Covid has.