FWIW

I know from personal experience that film prints dont come in standard length size when they hit the theatres

Negatives might be different

But Ive seen some reels bigger than others straight from the studio, seen movies come in anywhere from 5 to 10+ reels, and depending on their print source.....matching up one print to another to exact frame numbers can be quite difficult given that the projectionist often if not always makes splices that cut off different number of frames on each reel, and depending on their setup, splices them together......not always in a seamless fashion

By the time a theatre is done with the print, since most of them get treated like crap and get subjected to things happening like the film sliding on the side of a roller causing a scratch or hitting the grate in the projector causing a almost constant scratch or my favorite.....a brain wrap where cutting and splicing the print is done, often a few frames out

So hopefully the studios have an unused print source instead of relying on returns from theatres