Actually, if you've owned Lexus cars for any length of time, you will know that these creases turn into cracks in a couple of years and may even split/tear after about 5-6 years. It's unfortunate but, having owned Lexus cars for 15 years, I've seen this in all their cars except the LS series (for some reason). I wouldn't be too quick to get it replaced under warranty as the replacement seat cover will just do the same thing. If you bring this concern to your dealer's attention now but offer to wait a year or so "to see if it gets worse" (it will), they should replace it for premature wear but you'll get a couple extra years out of the replacement.
Good luck!