Firstly, I stand corrected - it is indeed now "possible" (with a little coercion)
.
Here is why I didn't think this was possible (other than I know it was only recently added!). When I went into the User Categories editor, the category filter still only had the four elements that the OP mentioned. So I just "assumed" nothing had changed in that regard.
However for my own test now, I just followed your directions, created a custom column with template {title} and went back into the User Categories editor. Now the dropdown not only has my newly added title custom column, it also lists all of my other text type custom columns that I had? Note that I hadn't gone through and ticked the box for them in the custom column dialog (I wasnt aware of this functionality until now). However until I did tick the box for my new fake {title} custom column, they didn't appear in that dropdown?
Expected or bug?
I'm wondering if I need to enhance my User Category plugin at some point now too - since the criteria of possible stuff to add is now much wider...