I would not over-read into that doc. In practice, the only missing stuff are extreme edge cases of the type that is actually not consistent between other implementations of bash.
In practice it works great. I haven't seen a failed command in a while
Incompatibilities don't matter much provided your error messages are actionable - an LLM can hit a problem, read the error message and try again. They'll also remember that solution for the rest of that session.
Because bash is everywhere. Stability is a separate concern. And we know this because LLMs routinely generate deprecated code for libraries that change a lot.
I've been working with the shell long enough that I know just by looking at it.
Anyway, it was rethorical. I was making a point about portability. Scripts we write today run even on ancient versions, and it has been an effort kept by lots of different interpreters (not only bash).
I'm trying to give sane advice here. Re-implementing bash is a herculean task, and some "small incompatibilities" sometimes reveal themselves as deep architectural dead-ends.
That's a lot of incompatibilities.
LLMs like to use the shell because it's stable and virtually unchanged for decades.
It doesn't need to worry much about versions or whether something is supported or not, it can just assume it is.
Re-implementing bash is a herculean effort. I wish good luck.