Different singers will have added different things. Some may have made up whole new tunes, but even then it would be to a song they had learned from someone else. Other traditional singers surely must have composed entirely new songs - but that doesn't necessarily make the songs "traditional", unless they enter the tradition.

In the case of "The Recruited Collier", even if it hadn't been embellished by Bert Lloyd, how can it be said that a song which exists in only one collected version from a single singer is "traditional"? In what sense can it be said to have entered the tradition? (being taken up by the folk revival is an entirely different thing). It is no different from any other composed song, especially one which copies traditional forms - it has the potential to become traditional, but hasn't yet got there.

Dick, you say the Recruited Collier was accepted as a traditional song - accepted by whom? Accepted perhaps by those who didn't research its origins, or who took Bert Lloyd's information at face value. In the light of more information about the song, it now seems that the original acceptance of it as a traditional song may be incorrect - which doesn't alter in the slightest the fact that it's a bloody good and deservedly popular song.

In a very few cases a song may pass through the tradition unaltered, but that's unusual, for the very reason that SOP so deplores - that in those cases the singers are acting as mere passive carriers. In most cases, however, they will add something as they pass it on.