The claim was that Rust is "heavily influenced by FP"; I think that's clearly the case, while "Rust is FP" is probably not (which case you make pretty well).
We might argue it's influenced by FP indirectly because those adopted features from ML etc also jive well with functional programming, for example pattern matching as a control flow construct...
It's true it's arguable. But if we start calling the languages that adopt FPL pioneered features "heavily influenced by FP" we end up putting a lot of languages in that set, like Java, Python etc for having GC and closures. So in order to use that as a distinguishing feature I think it's warranted to make the distinction.
