the "killer B's" originally referred to Greg Bear, Gregory Benford, and David Brin

I think that was later ... In the 1980s there was a surfeit of B-initial SF writers (as in the article's picture).

Also there was some media noise about killer bees, and they became part of the standard dungeon zoo, I think. Plus, possibly just "the Bees" would prompt "What, the Bee Gees?", a terrible risk.