There's an interesting difference between:
If he didn't already have a girlfriend, I'd ask him out - here we are
considering present policy: he has a girlfriend, so I'm not going to ask him
out.
If he didn't yet have a girlfriend, I'd ask him out - here we are in the
past: my habit was to ask out those guys who hadn't found themselves a
girlfriend.
P.S. The first formula can have the second meaning, but the second formula
can't have the first meaning, in my view.
https://reurl.cc/44drkK