We've seen b before. React was controversially released with a similar clause and ultimately Facebook dropped it and used a standard open source license. Their lawyers really love this idea for some reason.

Was it released with it? Iirc they tried moving to such a license from bsd, which contains no patent grants whatsoever, and hence they thought it was a strict upgrade. The community did not agree so they moved back.

Do their lawyers love the idea? Hard to say. My guess is, Zuck really likes the idea, so he keeps directing them and their chief counsel to try stuff like this.

It's almost as if having a CEO of a company placed beyond the control of the corporate board is a bad thing.