"The reason that didn't happen, ironically, is the same reason people still sing those songs in their post-Bert forms - unlike most folk singers, Bert Lloyd was a damn good writer, and when he rewrote a song it stayed rewritten."
correct, he improved the tradition, this is something that has happened to trad songs for centuries.
generally speaking improvements to the tradition that are not good, do not survive, the "folk" sort that out, so why all the fuss about "Bert",
Scholars are well able to sort it out,and singers like myself consider the merit of the song slightly more important.