This is my understanding.
Piano V2 is modeling different pianos. It's a Piano plug-in, but just like any other software or hardware pianos that use psysical modeling synthesis to create the sound, then it's in a way a syntheziser.
Any piano that's not a real piano is in a way a syntheziser, including the sampled pianos, as sampled pianos also use some kind of synthesis.
But when sold, one will not call for example Piano plug-ins for synths. A string keyboard is'nt called a synth either and so on. Only plug-ins, that we call synthezisers is sold as synths. But in a way they all are. SOme are just more or less specialised to emulate a certain known instrument or something like that.
If you don't wan't any synthesis used, then you need a true acoustic piano, and only use it without adding anything electronic - including any effects. One can even ask, if a acoustic instrument truely is acoustic, after it has been recorded, and then being played back, as any electronic equiptment including recording equiptment and playback systems add something to the sound.
https://en.wikipedia.org/wiki/Physical_modelling_synthesishttps://en.wikipedia.org/wiki/Sample-based_synthesishttps://en.wikipedia.org/wiki/Acoustic_musicThere are different kinds of synthesis. Anything that can be used for it.