2 reasons I can confidently disagree: 1. Unlike desktop platforms, most android devices cease receiving "official" updates long before the chipset stops receiving updates, thus maintaining them requires an alternative rom. While most people will just buy a new phone, the percent usually on the fence about something like switching from Windows to Linux are gonna be pushed harder into looking into alternatives. 2. Well over 1% of desktop users use Linux. Even if you debate the methods to get the current 4%, there's simply no debate on at least 1%.
The two combine to suggest that, on android, there's a very good change that more than 1% of android users are using some rom, and all roms help each other.
Don't screw up your otherwise valid argument by trying to "put tech nerds in their place" like that. These roms do matter, even if the judge 100% didn't "screw up". Everything else you said is both true and important, and probably matters more than what parent wanted, but it doesn't diminish the value of the roms, just suggests that parent was misguided.