This is a very frustrating but interesting thread. People keep repeating over and over two facts which are not really connected. What Bert did as a performer surely we can't question, he altered/improved songs which we all do. If we don't we're simply walking museums.
A totally separate issue is his behaviour as a scholar and writer. Here he followed the very ancient tradition of fabricating songs from oral tradition....Percy, Scott, Ford, Cunningham, Buchan, Baring Gould, Tongue, Niles, MacColl.....He was equally naughty.

Someone asked for more examples.
I'm from Hull.
Bert went out on a whaler from Hull and claimed to have learnt a version of the shanty 'Heave away my Johnny' from a seaman off Stoneferry in Hull.

One verse runs 'Fare ye well, ye Kingston girls, farewell St Andrews Dock'. Nobody from Hull (With the sole exception of one Mike Ramsden)would ever call anybody from Hull 'Kingston'. The only things called Kingston are the stadium, a few local firms and a rugby team, but even they're either Rovers or KR. Kingston stadium is KC. Most people from Hull can't stand the bloody name Kingston. St Andrews dock is a relatively new dock and would only have been built a few years before Bert was sailing out of her on his one trip whaling on a very modern boat. It was the fish dock, now filled in.