They dont care about security; only about control.
There are hundreds of millions of outdated Android devices that all Google attestation systems consider secure even though they all running Linux kernel that was never ever updated and can be rooted by anything.
Now try to install your own firmware on them without said outdated kernel... How dare you.
Technically the security works, just for their threat model. An exploit would need root and root means you likely cannot pass attestation AFAIK. The fact that this same exploiter can download all your contacts photos and texts is immaterial to, say, Disney, who want attestation only to prevent ripping of their content.