>It’s hard to delineate which of these are Chrome features or actual web standards. And it’s therefore hard to blame either Safari or Firefox for not supporting them if they’re not standardized yet.

Maybe you don't realize that Apple is on the W3C board that gets to decide which APIs become standards, so they can squash any API that they think could cut into their app store. Citing Firefox as some kind of evidence doesn't take into account the abusive business tactics that Apple uses to force developers to create native apps on their platform.

I don't care about Firefox does, because they aren't forbidding an entire platform from using any browser engine except their own browser engine, which Apple does with Safari on iOS.

So Apple controls iOS browser engines, and they also control which APIs get to become standards. This is plainly abusive. It's also part of the reason Apple is being sued by the DOJ

https://www.justice.gov/archives/opa/media/1344546/dl?inline