The 6 week vaccinations certainly sound like they would have been done by the breeder, so I would say go for it - you have nothing to lose. They may not be interested in the slightest
but at least you will know you have tried, but they may be delighted to get an update on their pup and to know that he has found his forever home
- you won't know the reaction until you try.
Honey had her first vaccinations at 6 weeks (by the breeder) - it depends on the vets and brand of vaccine when they are given, I think...