We used to plaster when a sand/cement screed was going to be laid and keep the gypsum plaster above where the level of the screed was going.
Any tanking/damp issues the render would be taken up a metre high from the floor with a intagral water proofer.
aye i know,i was just saying like .
even damp courses(s&c with waterproofer or dry coat ect) need to be off the floor,with wood/concrete/screeded/asphalt ect the plaster should be off the floor.
unfortunately i have had the unplesent business of plastering many damp coarses,more so in the 80s,hate the god dam things,would rather grout 500m2 of floor tiles with black grout