Larger sum won't make him work faster, but it will motivate him to keep working on this game.
As long as he would not hire assistance, you can't assume that update speed is lineary connected (don't know if that's the correct English term) to the sum he earns. What I mean is - if the sum multiplies by 2 it doesn't mean the speed multiplies by 2.
Also, you can't assume he has 1500 Patrons from the very beginning of the game's creation. He started with 0 Patrons, as every other dev.
P.S. The guy that told you if you donate he'll work faster was just kidding...
IIRC his story on hiring more help has changed, hasn't it? He originally said that he would be able to hire more help when he got more on his patreon, and after he surpassed that level he said he can't hire anyone else because he's too perfectionist.
It's whatever at this point, but after a few years of following the patreon adult games scene, I think I'm pretty well disenchanted with the entire mode at this point. The cost-to-output ratio is all off. I wouldn't mind paying a monthly cost ending up at a premium price to ensure good content gets made, but as far as I can tell the only people who actually have a track record for putting out finished content are Eva Kiss, Philly Games, and Sierra Lee. Everyone else seems to slow and then stop, whether due to scope creep, poor management, or inexplicable misfortune. I've spent a good chunk of change on this stuff, so I feel pretty justified in my assessment.
In fact, two of the three of those are women. Maybe that's the trick. Get more women in this industry and see some progress made.