I've never played an organ, so I have no idea what organ keys feel like or what proper organ technique is comprised of, and I'd never say organists didn't have "proper" technique. I was only responding to Woebot's inquiry insofar as he said he wanted to use a synth to "learn to play." Weighted keys make a huge difference in terms of feel--without weight, the "attack" on individual keys (as Guybrush describes) can be too fast, and it can make your playing sound halting.
I'm not sure about the difference between semi- and fully-weighted keys, but I do know that my Korg's keys feel equally as weighted as any piano I've played. I was a classical pianist for 14 years and played competitively, so yes, technique and feel matter a lot to me. If Woebot wants to learn to play keyboards with the intention of someday learning, say, Debussy or Satie, I think he'd do best to invest in weighted keys. If he just wants to pick a synth based on the sounds it makes so he can press a simple arrangement as part of a song or recording, that's different, of course.
In my mind, there's no way to "play" a keyboard that isn't two handed, and I would always prefer a keyboard that's a 4 voice + poly, either, for the same reason.