This rule does not make sense involving responsable breeders in the EU.

We (responsable EU reeders) have pups that can travel savely in the EU without danger for Rabies, since we take all precausions and keep all the rules. 

The puppydealers called  "breeders" that bring illegal trucks and cars full of pups from out of the EU are the once that bring the EU countries at risk for receiving Rabies and other diseases !!
They cannot be stopped by this rule !!!!

And very important...pups need to get bonding and social interaction from 8 weeks of age with the new owner(s) and new living -surroundings To do this from 15 (!!) weeks instead of 8 weeks can give major problems in several (more sensitive) breeds. It's far from healthy for the pups to stay this long in their birth house And in case several pups from the litter have to stay, major spontanious dog fights are happening with pups of about 14 weeks or younger even, in this unnatural situation to stay together at one territory at this age.