Those automation curves actually get sent to the synth as discrete events, with the rate depending on the output buffer length: there may be tens of millisecond

Those automation curves actually get sent to the synth as discrete events, with the rate depending on the output buffer length: there may be tens of milliseconds between updates. Plugins have to implement their own smoothing functions to get natural sounding results. This is one good reason to run your DAW at a high sample rate. The difference here to the analog domain, where you can continuously modulate any parameter at audio rate or higher with zero latency, is obvious. Of course softsynths own inbuilt modulation sources will be oversampled these days along with everything else they do, which is why they sound pretty good now. The Oramic is presumably using some kind of filtering on the output of those photodiodes or whatever it has, for similar reasons, but the point remains.