This could be a subjective feeling with no real data to back it up.
People say same about Go as well that it's type system and limited feature set makes it the best AI friendly language but there too, it just seems like a hunch rather than a proven fact.
If we are gonna go down that rabbit hole, then the natural conclusion is Haskell.
Well those people are simply wrong. Go and Rust type systems don't even remotely compare. Go types suck.
The thing is that this argument doesn't work with Go because its type system (and the whole language, really) is much less expressive and compiler gives a lot less feedback to the LLM. So it tends to have to write more unit tests and do more cycles of testing (and spend more tokens) to get it right.