If everyone sent cocktails/booze while seated in F back to coach....

I don't see how this is PMUA/PMCO (I get the they used to allow it portion) as much as thinking that since you were originally in F but seated in Y somehow there was an entitlement to share the amenities.

Should a FA allow you to discretely switch seats etc? Yes. But asking to comp liquor because someone in F doesn't want it is kinda tacky but what do I know.