I have main as a dependency.
I don't really have a Bairdotr character, I just picked that as the first dialog from the main campaign that I found. It could've been any other dialog.

Interestingly, I've resolved the issue, although I'm not -quite- sure what did it. I was experimenting with some other things, mostly involving copious amounts of rebuilding and re-generating Definitions, and rather to my surprise, it worked!
Right now, DB_Dialogs() by itself works as expected from the video, without my needing to use the default dialog field.