I think most of those are less of a scam and more just people severely underestimating the amount of time and effort it takes to make anything good, as well as overestimating how easy it is to actually make money from an adult game.
Unless you got in while the getting was good, or have something with obvious high quality and appeal, you're probably not even going to make $100 off of the hundreds of hours you put into a game. Pretty much guaranteed to not even make minimum wage, much less livable wage, when accounting for costs (commissions, gfx cards, etc).
It's easier than ever before to make a game - and with AI art, possibly even easier to make a decent-looking game - with most barriers of entry completely ripped out. So you just get a lot of optimistic people that don't realize how brutal it is trying to make the next BAD or Milfy City or whatever.