Very true, me saying they're totally isolated isn't 100% correct. That's sympathetic resonance, and other details like the pedals also slightly affects the resonance and pressing the pedals may be audible in a quiet/intimate recording. It's very subtle though and probably not noticeable by anyone who doesn't have lots of experience with a real piano. Many modern piano libraries actually do model/sample those properties though (I have no idea how).

While we're on it, drums aren't totally isolated either, they affect themselves. A snare roll is slightly different than just playing many snare samples rapidly because of the chains on the drum, and heavy cymbals also take some time to build up momentum so the first hit and tenth hit will sound different if it has not settled. These are all very subtle though compared to something like a guitar or violin or trombone where transitioning from one note sample to another sample digitally can be very obvious.