I don;t think it is DNA testng--not sure how they sex them, but I've heard of way too many that weren't pullets, that were ordered and paid for as sexed pullets to think they use DNA.
Meh. I could have sworn I found a page that said they did because of the demand, but I'll be darned if I can find it now.................. *sigh* So, it's essentially a crap shoot even if you order pullets unless you get older kids and know what they actually are.