His point is that in the world of programming languages, "true memory safety" isn't really something achievable without making it impossible for your language to interact with things like native libraries or the OS. Given this, the concept of "true memory safety" isn't a useful one. In general when you say a language is memory safe, there's an implicit caveat that there may be explicit escape hatches. No language (except perhaps web-based JS) is "memory safe" by the strict definition so it's not a useful parameter to use when talking of languages. You instead use the weaker version.

Terminology matters.