here is how it has to do with the original question...

poster wonders whether the penis is too big (length). other member answered replying

"Also, reminding them that not all of it will go in--and that if a woman can stretch to push a baby out, well...."

then your reply...

"Also when a woman pushes a baby out it does not lengthen her vagina, it stretches the walls of her vagina in width."

then my reply giving the info that a womans vagina does stretch in length.

all posts in thread relates to original poster in that their length of 13 inches is not too long because a womans vagina stretches in width and length.

hoped that has clarified the line of relating to the original posters question.