You've never seen a koikatsu model coming with animations. poses, and facial expressions? Have you even booted up the software before?
Poses and facial expressions aside as i do believe they were manually made using Chara Studio via HF patch, all the animations i've seen from this game already come preinstalled with koikatsu. You can literally boot it up right now and see for yourself.
And yes, i have used renpy to make a game. I'm currently experimenting with a VN project i have that's all AI ran and uses a dynamic system to progress to other scenes.
Now, i have to clarify one thing. I didn't come here to completely shit on the dev's ability to create a game. I do believe he has a knack for making a proper VN with RenPy.
All i'm saying is that 4 years for update is a tad bit too long of a wait considering he's still making bank in his patreon. All i've seen so far from his discord is that he frequently uploads update previews for the next major update. I think that deserves even just a slightest bit of criticism.