Yard isn't a dwelling unit. The rules for 551 could be counted on if there is more than 1 outlet since this could be counted as a "rv park"
I don't see a way to get rid of the GFCI requirement for outdoor receptacles between 15 and 50 amp, 120 to 250V.
210.8(A)(3) if at/on a dwelling
210.8(B)(6) if not at/on a dwelling
210.8(F) for dwelling and associated accessory building outlets
I you want to argue that a post mounted receptacle in a dwelling yard isn't covered by 210.8(A), then 210.8(B) would cover it.