Out of curiosity, I just went and looked at a few 135 neg pages from different cameras. Predictably, the Leica negs are perfectly evenly spaced and have the inter-frame space aligned between perforations, the Nikkormat is almost as perfect (fractions of a millimetre) in even spacing and also always has the inter-frame space correct. The cheapest 135 that I use is a Olympus Mju-II and this has slightly less regular spacing than the Nikkormat, still well under a millimeter variation though, yet still always has the inter-frame spacing between the perforations.
I did shoot once with a plastic disposable camera, one of the 'waterproof' holiday things, but can't find the negs right now, oops, though it would certainly be interesting to find out how that performed.
It seems that perhaps there are some cameras out there which have been disassembled/reassembled incorrectly, in order for the relation between the frames and the perforations (or better to say, between the teeth of the drive shaft and the edge of the frame) to be out of adjustment? Then again, unless we are relying on the perforations for precise slide mounting, is this really any problem?!