TServo2049 said:

If the negative was A/B, that would mean the yellow blobs are printed in, but that doesn't make sense. For one thing, it would mean the cement was actually light bluish-gray, which seems odd. More importantly, it wouldn't explain why different sources made at different times have different marks. They wouldn't be ungluing and regluing the negative multiple times, if the splices are printed in from negative then only the shots which were replacements would have different splice marks. The more I think about it, the more confused I get...

Perhaps what we're seeing on other prints like the Technidisc SWE for example might just be repairing of a worn out print, different from what we're seeing on the JSC print. I think the glue blobs at the end of shots in the JSC print have to stem from the fact that Star Wars is an A-B cut negative but I still can't wrap my head around why that IP ended up looking as it does.

For those who don't know how an A-B cut negative might be laid out and how it works:

Excuse the poor quality of the image. Anyway, the way it works is that you put all the odd numbered shots on one roll with a black opaque leader between each shot and the even numbered shots on the other, again with black spacing in between. When roll A is printed to the positive there will be no exposure where the black spacing is and where it ends the exposure from roll B starts.

As for those black marks you wondered about earlier, TServo, they do indeed appear elsewhere in the film. One classic example is right before the death star chasm shootout, as they appear inside the intended framing.

Probably a result from the optical process.