8 days post op DJS - 1-2mm midline shift. How do i know if its skeletal or dental?

Hey all, looking for some outside perspective here.

Background: Had bimax surgery 8 days ago — 8mm upper advancement, 7.5mm lower, 2.4° CCW rotation, 1.5mm downgraft, to correct a 4mm underbite. Everything seemed on track, but I've noticed my midline is off by about 1-2mm.

My ortho gave me elastics to help correct it — triangle on the left, 4-3 box on the right. When I asked my surgeon about it, he said "1-2mm is generally accepted," which is reassuring in terms of magnitude, but doesn't actually tell me why it's happening.

My concern: I understand elastics can correct a midline if it's a dental/positional issue. But if the underlying cause is actually skeletal (jaw bone slightly rotated/shifted vs. the plan), wouldn't elastics just be moving my teeth to visually mask that, rather than fixing the real issue?