Heap allocation doesn't really come up all that much in "101" programs, though. You have Strings of course, but that's about it. So I think teaching Rust could work, people just haven't gotten around to trying it. Most intros to Rust including the official book explicitly assume familiarity with some other programming language, and often fail to explain other things (at either the "low" or "high" level of semantics) that a 101 student wouldn't know.