What I wonder is: how does that compare to the alignment that was there before the stuffing was done?

I have strong doubts that many frames out there are very well aligned, and we don't seem to mind. For example, many of the older frames I've had have more than their original 126mm spacing - the back end seems to spread out from use over time. I really doubt that this happens evenly.

I'm not questioning you well biked, just curious. Have you measured alignment before and after spreading? Was the frame in alignment before spreading, and if it wasn't, did the rider notice?