There seems to be a concern that Apple will use these requirements to ban every single alternative including Blink and Gecko. I doubt that is the case since the purpose of these changes is to allow reliable, responsible players to run their engines on iOS without giving the keys to the kingdom to every app that requests it. Banning Google or Mozilla would not satisfy the EU requirements. Banning BlinkButItAlsoMinesCrypto is fine.
The only additional thing I'd want as a user is transparency. I want to know if an app with a WebView is using WebKit, Blink, Gecko or EngineNobodyHasEverHeardOf.