Since you went to all the trouble to make that picture, I will go to the trouble to point out that the nuts on these basses don't line up. They don't appear to all be pictured at the same scale, so I'm not sure your drawing means much.
I understand exactly what you are saying. However I have made quite a few pictures like these over the years where I carefully scale the pictures so that the nuts and bridges line up perfectly. Typically when I do that I find that all the intermediate frets fail to line up and when I do that with several basses as in this picture the results are pretty comical since sometimes no two of them agree. How can this be? The answer, near as I can figure out, is distortion in the camera lenses that were used to take the pictures. If you take pictures of two 34 inch basses and scale them so that the nut and bridge line up then every fret should also line up but typically they do not and very often some will line up and others will not! I don't know of anything other than lens distortion that could cause this to happen and one time I used the distortion functions of a photo editor (Gimp) to try to correct the situation with pretty good results but boy was that a lot of trial and error work! So, in this case I just scaled the photos so that the distance from 20th fret to bridge was the same in every case. I believe this is the best one can do without an extreme amount of effort and it should be reasonably accurate since the amount of distortion difference from bridge to 20th fret in the original photos should be smaller than that from bridge to nut and therefore the accuracy of the picture above is likely higher than if I had equalized the distance between nut and bridge. But for the purpose of this discussion it is likely that either approach is accurate enough.
But kudos to you for noticing, no one else ever has!
