The point about a zf is that the string is always the same height above the fingerboard at every fret, so an open c-chord should feel the same as a c-shape 'd' with a capo on the 2nd fret(save for the inevitable extra pressure due to the slightly higher string angle).A full-bar F shape should also feel the same as further up.

I've encountered 'nutted'telecasters etc. where the action is harder at the 1st fret than further up,possibly giving a slight pitch problem as a result of greater downward bending(the string,not me).

'Cop-out'?.Possibly,but the builder still has to cut a nut because the 0 fret will only give an up and down string break-not side-to-side.
Cheaper instruments? Didn't the old Gretches use a zf?