Apple or Google don't ban URLs or websites on their Safari or Chrome browsers. Is that due to historical reasons or are there any laws regarding this?
With the recent push for PWAs, it will be interesting to see if communities like artstation use these instead.
They could add editorial policies to those criteria whenever they wanted. Or change a line of code to turn a drastic warning into a full block.
Android OS/iOS => Chrome/Safari
You are confused between the distribution platform and the client. It's ISP/Play Store/App Store's job to do filtering.