The only reason pedigree cats stay with the breeder till 13 wks is because its GCCF rules. Some behaviorists feel that this is too long, especially if the kitten ISNT properly socialised while at the breeder, which of course can happen. Breeders that have quiet homes, or bring mum and kittens up in pens away from the household probably won't have properly socialised kittens, wheareas if they'd gone to their new home earlier during the main learning period (between 2-8 wks) then they probably would be better socialised.