Michael does that matter? ,it could be argued that all tradtional songs evolve and get added to, that is part of what makes tradtional songs differ from recently composed songs,
recently composed songs generally have their lyrics copyrighted, that means in practice they do not evolve, that is why recently composed songs are not tradtional even if they are in a folk style,
an example Yesterday" lyrics are in my experience always sung as Paul MacC   wrote them