Earlier quoted context omitted.
For Android w/Playstore you can set up a child's account through Google and then use Google Family Link app to control app downloads, block specific apps, and set content restrictions for apps, movies, and games. You can set down times for the whole phone and lock it remotely which is of huge benefit for bedtimes!
That's parental control, that's not the same. I want to hand my phone to my kids and let them access only one or two apps that I have listed as allowed. I don't want (yet, but it will come) for them to have their own device that I control as you explained.
i don't think multiple account is an /e/OS feature, but must be coming from lineage/ASOP so other ROMs should have it too (unless it was intentionally removed)