Hello, you are through to Dr Linda, a UK based vet.
Congratulations on your new pup Tweed!
It would be incredibly rare for a well-bred pup to be re-homed any time before 8 weeks. Most are still drinking regularly from their mother at this age and receiving her antibodies. If the pup is fully weaned from her, we would want to ensure they are eating well and gaining weight each day. As they will have low antibodies without their mother's milk, we might discuss vaccinating him from 7 weeks. This is something to discuss with his future vet and will depend on the brand of vaccine they use.
This is also a very important age for socialising with siblings and learning 'doggy body language' and boundaries. If Tweed is interacting well with his littermates, this will be really critical for his development and is something I would encourage up until at least 8 weeks of age.
Would it be an option for pups to stay together away from mum (if she is fed up) until 8 weeks? I would ask the breeder this.
If this is not possible, you could go to view the pup.
In your situation, I would make an assessment after seeing the pup. Are you happy it is eating well and robust? Does it seem confident and social? Etc.
As I say, for the above reasons it is not ideal but it could potentially be ok under certain circumstances.