What worries me is every app that's not a dedicated browser suddenly including an entire browser engine (the way that every app on macOS/Windows now does). Apps will import one version of Chromium and then not update it for *years*, long past the point where it contains security holes and lacks support for new platform features.
Steam on Win/Mac/Linux is still using Chromium 85! That's 2 years old, and it's a piece of software under active development.
I know of an actively-developed Windows game using CEF 3!!
In other words: do you want your favorite bank/airline/restaurant/government agency's app to be 100+ MB bigger and contain a growing number of vulnerabilities? I don't, and neither does Apple. If this goes ahead, I hope the App Store rules around it are thorough. Shipping a browser is a huge responsibility, one that most organizations are not prepared for.