iOS does not allow third party browser engines. Every browser you download from the iOS App Store is using 'Safari Lite' under the hood. It's ostensibly for security, but it's more about control.
The security angle is easy to understand.
Not sure why Apple cares about control.
But it easier just to want to make Apple seem bad, so there's that.
I would bet Google's track record would easily allow them to defend this in court. More an issue with Google though.
And the problem isn't abstract. Safari lacks a ton of very useful API implementations. Like, try programming a QMK keyboard on an iPhone: it's literally the only platform in the whole world unable to run the Via web app.