I can't see this being useful; the amount of energy generated is just so far below what's practical to use. An equivalent size of solar panels would be cheaper and provide orders of magnitude more energy even when it's cloudy.
It's an interesting idea though, and cool that they were able to harvest any power at all.
If this isn't just an artifact of the way data was collected, I suspect it's not because Linux users are more likely to install alternative launchers, but because they're much less tolerant of non-FOSS software in general.
Anecdotally, most Windows users I know use a custom launcher, but they use proprietary ones like CurseForge or Feather (both of which show advertisements; something no self-respecting Linux user would accept, but which has been normalized in Windows).