Ithaca If you observe the mechanism in an acoustic piano, the only thing the standard sustain pedal does is lift up all the dampers. In an acoustic, as soon as you lift the dampers, all the strings - even the ones you're not pressing - are free to resonate, so you'll also get what I think of an aural shimmer (or sound aura, or sound cloud, depending on my mood). And the quality of that sound depends on the piano. I don't know if your digital will do that; mine certainly didn't, but it was a very elderly Roland. (It was the first of the really good actions, but the native sound was meh.)
Today I tested my Roland FP-30X's built-in sound engine, and I'm surprised it actually does have sympathetic resonance. If hold down C2 silently, strike C3 then release (no pedal), the C2 will ring for quite a while as it remains held down. Same if I hold down G2 then strike C3, although the resonance will be weaker. I used to think sampled digital piano sound engine cannot do sympathetic resonance, and that would be one big reason to use modeled sound engine such as Pianoteq. Well, technology has apparently advanced that even mid-entry level DP now have this feature.