I believe what's being suggested is that `cargo audit` should be a part of cargo rather than an add on.
You'd obviously already have cargo installed, which means you should be able to run a command against cargo to see if you are currently exposed to any security problems. Even if it's not the current "audit" add on.
As someone using bazel at work, the find script was much more amenable to me trying to audit our usage - we don't use cargo, so no cargo cache or cargo audit, but I can still figure out whether a particular package was downloaded.
If you're using a different tool then it falls to that tool to address the same problem. The point is that I shouldn't have to already know that a compromise has occurred and then go looking for it manually. The tooling should automatically start shouting at me very loudly that something happened with one of the packages I'm using.