none said:

As there are laser bolt fire frames before and after these modified ones, which don't seem revised (?) why change these three? Guess it's more dramatic having the bolts near the rebels heads... Some occurances of laser bolt fire being changed for the SE have coincided with another type of revision either in the same shot or neighboring scene. This catch seems to add weight that everything was recomp'd.

Yeah, it might. There are more than just these three I posted in that particular shot that are re-comped, probably all of them, these were just the most obvious ones, that's why I decided to post just these three frames.

I was a little sceptical about it before, because all the timings and positions of the elements seems to match the originals so precisely, whereas in all other cases of re-comped shots in the trilogy, you'll immediately see the difference if you studying it, this may all have to do that the positioning and timings had to match the on-set footage in this case with all the blanks that is fired.