Since most of the feet are designed for a zig zag machine, I selected a Pfaff 130 as a test bed. The snap-on ankle fit fine.
The foot fit perfectly and the Pfaff's needle came down in the center of the needle hole. Stitch quality is just as good as with the Pfaff foot although I am not getting a full width zig zag - apparently, my 130 needs a drink of oil.
Bouy'ed by the zig zag test, I swapped the zig zag foot out for the straight stitch foot to make sure the needle would line up with the hole in the foot. It matched perfectly and the straight stitch was as good as ever.
But one test is not conclusive, so I moved the ankle and strraight stitch foot over to a Singer Featherweight. As expected, the needle came down right in the center of the hole in the foot
and stitch quality was identical to the factory foot.