a friend of mine is curious about her newly acquired golden retriever pup as it has a small black tuft on its leg even though the rest of the coat is pale.
She's been told this is a good thing as it is close to the original retriever.

Is this the truth? Does anyone have any further info on this phenomenon?

It is not a 'good thing', as it is not desirable to have any clumps of black hair in the coat. However, it is not unusual for all Golden Retrievers to have a few black hairs in their coat and this is to be expected.

A pale Golden with this phenomonon usually also has excellent pigment, which is probably what is meant by 'close to the original Retriever'.

Snomaes

I think it means that the pup is throwing back to its ancestor, the flatcoated retriever, which has to be a good thing in anybody's book!!

Jo and the Casblaidd Flatcoats