The camera creates a mask or algorithm for stitching at calibration, so later on when using CamCap it will do the same stiching regardless of what the photos taken are showing.
So when you capture something thats (considerably) thicker than the original material you used to calibrate, you get this result.
I’m not saying this is a good thing, I don’t like it either.
Btw, camera capture is not accurate (yet).