If he has an SSD, it's a much faster solution to this problem.
If he has an SSD, then he should use it. Doesn't appear that he does have one though.
He hasn't mentioned one at all, and has not been forthcoming with what his system specs are, other than apparently it can run "other heavy games"... Which is about as descriptive and helpful for us as an inflatable dartboard.
That could be anything from Crysis to Ark: Survival Evolved.
HDDs have pretty much always spun down when they're not being particularly active, so the advent of SSDs plays little-to-no impact on that, and the "green" HDDs are nothing more than a marketing gimmick to sell lower speed/performance HDDs.
Other than potential issues with his HDD, insufficient RAM or managing to run out of VRAM has the same effect on even a Ren'Py game.
For all we know he could be playing whilst Chrome is running with 30+ tabs open at the same time, whilst streaming a 1080p 60fps video on Youtube, and he doesn't realise he's taxing his system.