I brought my pup home at 6 weeks. He's completely fine, no separation anxiety. My new addition who was allowed to go home only at 8 weeks because she was from a much better breeder (I got her at 2.5 years old) has terrible separation anxiety...so please, unless you have data that uses a huge segment of the population, do not scare people with things you've read online that have no basis except for an author's own experience.
If she's releasing the other dogs at 6 weeks, its probably better for you to get yours at 6 weeks as well. The point of him being at the breeder is more for socialization with the pups and less about the mom. She'll be around, but at that point not doing that much for the pups.