I think it really depends on the photo, whether or not the model had to hold a pose for a long time. For very early shots, sure, but the poses are typically very static for those.

I must admit, I haven't seen a preponderance vintage photos of deep backbends (this and this, and this being notable exceptions). Maybe I should look for more.

As for handpainted photos, well, they can be wonderful, and they can also be absolute trainwrecks. It really depends on the colourist. I've seen some terrifying colour jobs.