This is a very recent change that UA made to stop *Gs from entering contract lounges and is already enforced in BOM & DEL.
They also forced *A to change their *G lounge access policy from "all *G's in Y have to be given contract lounge access" to "all *Gs in Y may be given lounge access to contract lounges".
None of the other *A partners has followed suit as yet... but I suspect LH might be next to do this and AI at some point too.