What led Creighton to think this song was written for music hall performers? Are there any candidates for the "genuine sea song" the chorus supposedly may have come from?

Is there a reason Sharp's manuscript (titled "Here's to My Tin") from 1904 is listed as the earliest date on the Ballad Index? "When I was a young lad" from The Charmer feels close enough that it should at least get a mention. The only real difference is the lack of chorus. It also reads like it was meant for a different melody to me.