For the record, I've seen this happen very similarly without using any mods or custom races, as well as default settings (I used to only play that way). While it's not common in my experience, strange (and amusing) things certainly do happen sometimes with surrendering. Clearly another lingering AI problem. I haven't tried setting the threshold to "never" though.
And I'm not sure why you insist on being so dismissive about this, N1ghthavvk. Sometimes others come across problems you just happened to never encounter yourself. LH still certainly has its share of problems, and goofy AI is one of the most notorious.