It looks like they legally could not include the ROM waves or mention 'Wavestation' in any promotion. Steinberg's discontinued (Wizoo developed) Xphraze was meant to be a VSTi Wavestation clone, but Korg who was developing their own Korg Legacy plugin warned them off. Oh, here is a hint that's not commonly publicized. So short samples like drums were added to the single cycle waves, then they can be sequenced with pitch, crossfade and duration. What you were hearing is Korg (with Dave Smith on staff) upping the ante on the Wavestation with wavesequences you can program, though it's not really quick going. (Yamaha bought the dying Sequential and were part owner of Korg in those days) The Yamaha TG33 and SY22 were the stage in between. The core idea it's taking from the VS is to have a joystick mix 4 quadrants of waves and be able to record and repeat the moves. While it has digital filters, they are meant for the most part as tone control so I wouldn't connect subtractive synthesis to much to it.