I agree with @Hellzero I'm sure it's a product of the manufacturing process, not intentional. If it was intentional it would be curved like in the re-issues or at the wide end of original tuners.
I think I have the answer, looking at the photo that started all this off. Compare the two middle tuners:
Relative to the screw holes and mechanism, the plate on the D-string tuner is 'higher up' with a bigger gap between the top edge and screws tan the A-string tuner.
The A-string tuner is noticeably longer so that it contacts the E-string tuner, but the lower screw holes appear to be the same distance from the edge.
The lower edge of the worm gear on the D-string appears to align with the bottom of the plate, that for the A-string overlaps considerable, despite the plate being longer. It could be a trick of the camera perspective, however.
There are definite variations in the dimensions of the tuners that point to multiple operations using jigs or tooling that are not at the same settings, if not completely different.
A few minutes with a pair of calipers would sort it out.