Those are interesting points / possible approaches, however is there any indication that this particular project enables any of that?

This seems focused on signing binaries / build artifacts.

IMHO it seems like if you have the threat model of "crowbared maintainer forced to insert backdoor" you probably don't trust sources let alone binaries and need to vet your dependency sources and then compile your own binaries from them.

Many open source dependencies will not have a jurisdictionally diverse review team, or any review team at all (single maintainer).