"Memory safety" is a security term, not a PLT term.

That's a statement without source and even if it was widely accepted as true it doesn't imply the fact that something needs to be exploitable to be considered a security issue. We are full of CVEs without a known way to be exploited.

First off, in any and every engineering discipline it would be absurd to claim that "safety" only means security against intentional malice.

Second, the burden of proof goes the other way. It’s absurd to claim that UB is safe unless proven otherwise. Unsafety must obviously be the default assumption.