The warp and weft ( length of grain and width of grain) of the fabric does have a small degree of variation in the amount of stretch on the cut edges but not enough to make any difference when sewing patches together. I never worry about it. The only time I am careful is with directional prints that I want to lay a certain direction.
The selvage to selvage cut has more stretch than a length of fabric cut. Not enough to worry over.
peace