I have not owned blue jeans since the '80s. Recently I changed jobs and need 4 pair (at least) so I picked them up at American Eagle Outfitters. I always hated the stiffness of jeans and cycling in them was out of the question. To my surprise, the stretch (elastic?) built into the cotton weave makes the jeans feel like I am wearing NOTHING. I mean they are super comfy. No doubt the seam in the crotch could be an issue, but if you like wearing jeans I can see how you would adore these. I could wear them as pajamas or doing gymnastics. The spot in the crotch where the four seams meet is pretty flat! If you have a bike saddle with a cutout I can't see how that seam would be a problem.
On the tag it says "Extreme Flex 4". You should try them.
As far as how they wear due to rubbing on a saddle I have no clue. As I recall they were pretty cheap and always "Buy 1, get the 2nd pair 50% off. This is how I ended up with 4 jeans.
FYI, I have cycled to work in them but it is only one mile each way. They felt great for that short distance.
Cheers.