Sonic is talking about different samples triggered by velocity, so the sound doesn't just get louder but brighter, etc. Some of the dimension pianos use multi-sampled velocities, I think, to make them more realistic. You should ask Cake.
But that is more a function of the samples used than the synth. To achieve the same thing in Dimpro (w/ its true sample playback engine) you would have to go into SFZ programming or grab the text from one of the instruments that does muti-sampled voices via velocity. Actually, SFZ shouldn't be too hard, tho text-based control is hard to get into. Just as you spread the samples across the keyboard to trigger different samples, you tell the engine to play a different sample depending upon the velocity. The sonic boys layered 7 (? I think) different samples across every note and restricted the velocity that any one would play. A bit tedious.
Rapture and Z3Ta are synths, using a wavetable impression of a sample rather than the sample itself. I guess you might be able to do something like it, but I don't think the results would be organic.
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