Elsewhere in the thread, someone reports that with MTE enforcement enabled, there are lots of crashes. And app and system service developers don't seem responsive to them.

That's not something that's really acceptable on a $500+ phone... so if you're Google, you're not going to turn that on by default and you're not really going to be interested in keeping it as a feature that users can turn on.

Graphene has a different focus, so they can push the tradeoff towards enforcement and crashes rather than non enforcement and fewer crashes.

Google could perhaps do more with their crash logs and pushing app developers to fix MTE crashes, but they don't often do a lot of that; and they get called out for being developer unfriendly when they do enforcement.