I doubt that working on small casual programming puzzles is his only use for programming languages. I read his comment as saying that that's merely all he's used Rust for, so far.

Short-term and long-term stability are needed for just about any serious software application or system. They're useful to have even for short scripts that might be reused later on.

And he said he was "terrified" by C++. I explained why he shouldn't be. I'm not sure why you're getting worked up over that.