I believe the kinks you see are actually "gathers" caused by the stamping process. You notice them even more in nova tunnels where the excess metal is squeezed together,(gathered)into an untidy bunch, or ridge, or even stretched.
Areas that are not critical to exterior appearence are usually left this way in the stamping process. GM wasn't going to spend money on a dead smooth floor back then for something that no one was going to see. I base this 30 years of manufacturing experience, mostly in welding, but a few months in the stamping department.
