An AVN is not a game (N = novel). A game you do more than just read and fap. A real game uses Unity or Unreal, not Renpy. Sandboxes tend to try to be both an AVN and a game where you do more than read and click some choice boxes (if it bothers to have those, some devs skip it and just make it kinetic for simplicity's sake), but then it tends to do poorly at both. By your standards this forum wouldn't have 10% of it's current content.
Such empty .rpy's just act as a switch. In other words the incest names and dialogue are already in the code but just turned off without that file included. An easy work-around for Patreon/Paypal's bullshit censorship (0 byte "patches" don't get any smaller).
This one was weird though. Dude just released the first version of the game then completely disappeared from patreon. I honestly wonder if something happened to him.
Pfft, more likely he just made it for a cash grab from the suckers that sub to .1's and then forget about their sub = free money until their credit card expires and more common than you think if lowest teir is $1. Not bad for maybe a few hundred hours of work if you end up with $10k before the money completely dries up. Maybe about $30/hr average. That may sound cynical as fuck but as often as I see abandoned .1's that still have 400 subs after 6 months of nothing I'm starting to think alot of dev's start writing, posing, rendering and coding with this mindset.