How do I send/request resources from the AI ally?

...or am I wrong?

You are wrong.

Added 3 minutes later

;)
I don't think it's built into the algorithm. Most likely, the turn simply ended + there were narrow passages.

I understand that we're talking about passages that are one cell wide; otherwise, there wouldn't be any problems. And regarding the turn ending – it happened too often according to the theory of probability... Although, it could be a matter of selective memory; I won't argue... In short, an ally is an inevitable evil! :)