Yes, just like wav all NKS audio previews (= rendered snippets of the patches) are simple readable ogg vorbis encoded files.
For automated preset/patch rendering I recommend you take a look at PresetMagician (linked above). At least for the already supported plugins (and there are quite a few!) you get all the audio rendering freely delivered.
You can ignore all the NKS stuff - just grab the extracted audio files.
For any other plugin I believe there is no other way but via mouse/keyboard automation as you already did. In fact this is how some folks actually generate the sound previews for NKS libraries that are sold on the web (e.g. here:
https://freelancesoundlabs.com/index...trol-vst-packs)