It isn't fair to compare on either side. Having seen Kate M. out and about more quickly after her third, the public is getting to see her shrink down pretty naturally. That seems to be her body type and that is 100% fine. It also is 100% fine not to snap back as long as you are healthy.
FWIW, I have four, including surprise twins. I bounced right back after the first two, but the surprise twins wrecked my body. I got hate for snapping back, when I was really just working my tail off at work and eating whatever I wanted. Then, when I didn't snap back, I felt judged by society somehow.
How about we all just accept ourselves, try to be healthy, and stop caring about and judging how the other half (or 5% or whatever) live?