I was in Wickes last night and saw exactly the same thing. I think the
marketing department are having a laugh. Trade emulsion is what you
would use for new plaster, you just add some water to it. To sell a
paint specifically for new plaster is taking the ****.
Vinyl emulsion is more expensive and wipeable unlike normal emulsion
which would come off on a damp cloth.
Bathrooms and kitchens used to be done in Vinyl satin emulsion which
offer some resistance to moisture or oil based eggshell which was
scrubbable but they now have improved acrylic paints which they market
as for the kitchen or bathroom. As far as I can tell, these bathroom
kitchen paints are exactly the same as the water based acrylic
eggshell that you would use on your woodwork.