One obvious reason to have an LLM output a high level language even if you are never going to read the code is because it will require fewer output tokens and therefore be cheaper.
It's not immediately clear to me why having an LLM output code in JS or Python should inherently consume more tokens than C or assembly. I'd expect token usage to correlate with the complexity of the algorithm being implemented, not with what specific language syntax it's being implemented in.
But either way, token consumption is only a relevant concern if you still expect to be using SaaS LLMs by the time you're ready to have them target lower-level code for you.
If LLM-generated code continues the human pattern of having roughly the same rate of bugs/LOC regardless of language, then I also expect LLM-generated code in high-level languages to be less buggy.
Typescript is not meaningfully a higher level language than Java, C#, or even Rust. Typescript exists for exactly two reasons:
1. JS is a privileged language and allows you to tap into web and node
2. Type safety is good
But TS is not a good language overall. It's just much slower than alternatives and much less safe.