On the other hand part of the complaint in the main article is the lack of basic core utils at a standard that OpenBSD would consider. Or things that could be a base world dependency for them.
OpenBSD developers themselves did that, rewriting a lot of things that already worked. But they wanted to improve them security wise. So your argument doesn't fit with what they did already. Language is tangential here. Their main focus was security. So it's pretty reasonable to ask, why things can't be rewritten in Rust to improve security further.
Note, that the answer doesn't say that it can't benefit security, which would be a principal argument for OpenBSD. It brings side reasons as to why it's not easy to do (like integrated tools, developers' availability and so on).
For those who want the OpenBSD devs to abandon their many, many years of experience with C and instead adopt Rust, I think it's a fair question to ask the Rust folks why they haven't just started from scratch and built their own unix-like operating system. This seems to be a more reasonable approach that trying to force an existing operating system to adopt their language.
Oh wait, that's right, none of them has even gotten around to writing a replacement for ls, grep, .....
