In macOS, there is a security-policy layer of some kind on top of xattrs, separate from the security-policy of the file itself. `com.apple.rootless` is an example of an xattr protected by this mechanism: users (even root) can't apply or remove `com.apple.rootless` from files on a filesystem mounted as the rootfs.

With this mechanism, it'd likely be possible to give executable binaries an xattr containing the checksum, generated by Gatekeeper+Rosetta, that the user couldn't modify, while still being able to otherwise modify/delete the file. (And, presumably, modifying the file would automatically invalidate/remove the checksum xattr.)