Did you happen to see this?
At first blush it seems like wanting your child to have the opportunity to re-enact your VBAC with a doll is a boundary problem.
I did tell my daughters about having a VBAC fairly early on. I didn't use a doll, and I think it was age-appropriate. I haven't shown off my scar, thank you. That much detail, they aren't ready for even 10 years later.
What they know is that I love them both dearly, but the c-section was not a good experience.