Knitting through the back loop does twist the stitch, so if you’re trying to get the even looking Vs, in stockinette stitch it will look different. If you’re doing garter stitch, it’s a little tighter but doesn’t look all that different ( unless you look REALLY close).
Sometimes you actually WANT to knit through the back loop. Rice stitch is a decorative stitch similar to Seed stitch in which you P1, K1tbl, P1, K1tbl etc. on right side and do regular knit on second row. It’s used often in Aran sweaters instead of Seed stitch, but if you don’t knit through the back loop it doesn’t work as well. There is also a knit two together through back loop decrease I’ve seen used occasionally.
My great-aunt (who taught me to knit 40 years ago) always knit through the back loop and I was about 13 before a friend showed me why my stockinette stitch looked “different”. I never did tell my aunt. She knit dozens of sweaters and hundreds of pairs of mittens for charity in her 96 years and ALWAYS knit through the back loop!!