It’s shorthand for The Grand 3 SE.
Actually I have the demo, and was interested in upgrading either to full or to SE. I concluded that the SE version would suffice for the price until another solution comes, Eggs in 2 or 3 baskets ya know? 
No stacking, but big chords, long tails, fast music…
But yeah Piano is one of those things, so harmonic and rich, I don’t think it’s a game changer as far as a beautiful music piece, to use 16 bit, sometimes, I do prefer it (16) alongside other VSTi, as 24/32 bit stuff can sound too perfect, too shiny and clean.