Great suggestion.I don't know if I'd trust an iphone angle app for tiny changes, so many things can go wrong (eg accuracy/repeatability of sensor, slope of floor, both tires inflated properly etc.).
Does someone have a measurement from the axle back to a point on the bike? That should be more accurate.
Did they say how the swingarm dent happened? Inside looks to line up properly, but if you have a replacement, not an issue.