I'd agree it's quite a loosely organised grouping, but still pretty coherent. Comparing to anarcho-syndacalism is way OTT IMO.
I'm ambivalent on BLM fwiw, the initial 'movement' generated real momentum, since then I'd say it's done some good work and some not-so-good things, but claims that there is no BLM organisation and its just a slogan feed into some of the nuttier gammon conspiracies about the movement IMO