Lets see if I can explain it right. Guy here...
1 - Human cervix is relatively close to the entrance and is likely to be pushed. In fact any medium to large dog inserting the knot is sure to push and stretch everything quite some
2 - Cervix penetration is possible with small objects but supposedly quite a painful experience. I've seen a few videos of woman who would prolapse cervix and insert a finger or small dildo. (I personally would class those ones with male urethral penetration per pain/pleasure)
3 - The problem here... is the angle. If you see a cross section of a human female, cervix is aligned larerally, which will make it *very* difficult that the point actually gets inside, more likely will hit the pocket.
Not saying in can not happen given a proper push, move and shake and stretching, just... not easy.
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