Your guess very well could be correct, although I won't make that assumption. Even if he did approach the development of the game in this way- focusing on making the game easier to modify early on would have made it so much simpler for even himself to add new content, I imagine this would make his additions a lot more frequent while still upholding some sense of quality.
Yeah, I don't actually think he does it to make it hard to mod, it doesn't quite fit the theme of the... "awkwardness", for a lack of a better word, of how he've build and make the game, in ways that just makes it overly complicated for himself as well.
As example, it's odd how he choose to spend time seperating the different hues of the shades on some of the textures in TTG, like hair and skincolour, just so that you can change the colour of the shading; a feature that is extremly niche, but adds hours to the creation proccess on those parts; and even then he've taken the time to actually split the origional textures, when he could just have made the orginal be a "base", with the recoloured shades be an overlaping masking texture, which would have given the same end result, and saved time.
I do think that he might have had help with the coding at some point in the past, with parts he found difficult.
Now, he might just have replied like this, so that people would quit asking him; but someone asked him a while back on Patreon if he could make it so that the "discharge" would remain even after clicking out of that menu, and his answer was that it isn't possible with how the game is made.
I don't know anything about coding, but just looking at the DoAction files, it feels like it shouldn't be very hard to just... copy-paste the "Swelling" action, which have a progresive appearence, triggered by another action, add that trigger to "Discharge Outside", swap the texture and line it up with the discharge, and you'd end up with a "Discharge" layer that slowly fades.
I don't know, I just feel like nothing about him makes sense.