Although I would have serious doubts in the case of this dev, there also can be situations where multiple game development is feasible while not hampering the progress of the other games (e.g. you have one artist working on one game, another artist working on another, both working under the same development team)... so condemning ANY dev for starting a second game before they nearly finish another might be a bit too hasty in select situations.The only logical reason I can think for this is that the renders are the bottleneck on development.
That is, the author gets all the writing/poses/etc done, and can set the PC to start rendering. At which point you start working on the next batch of content and complete it, but still have your rendering PC chugging away.
So you start work on a different storyline...
However, that would only make sense if you were using 3d rendering in only a single game. Instead, that rendering work backlogs onto every single game in this scenario, and they all progress slower.
Which means the only rational reasons for juggling multiple game projects at a time are:
a) Inability to focus and complete one thing. Basically like ADD, but for programming.
b) Intending to make more money per month by having more patrons (due to having multiple games going at a time), which is SUPER sketch
c) Reusing renders across multiple games to "multiply" your output
d) Not actually caring about finishing any of the game, so you *want* progress to go as slowly as possible so you keep making patreon money as long as possible (easier to keep people interested than to finish a project and hope people stay for the next one).
I've cancelled every patreon plege I have when a creator starts a 2nd full project before the first one is 90%+ complete.
I would think a better rule of thumb is how much progress they tend to make on any game, rather than how many concurrent projects they have going on (within reason)... but that's just my opinion.