No, my rear doesn't suffer and no there is no big material tension. I have jeans as tight and they have not ripped in the crotch. Anyway, that is just your opinion. Like I said, if I wanted a looser fit I would have gone for Larkee.
Looking at them I am not sure they are real. I have never seen them with brown buttons. I have seen with gold coloured buttons though.
The 31 and 34 font is wrong too.
They are a good copy but they have things that are not quite right.
Do they fit the same? Can you show me how they fit compared to your other "real" 501s?