The idea that traditional singers only sang in pubs is incorrect

Just sometimes, and when they do... and its more about the "what" and "how" than the "who" or "where." Moving it to the kitchen or front stoop won't magically convert that forebitter to a shanty. That takes physics aka work.

The stage has come with its own maritime traditions since the days of Martial (artist) and Polybius (historian):

"The present Manager of the Chatham Garden Theatre, was formerly a Lieutenant in the British Navy. He was afterwards on the boards of the Norwich Company in England. He was principally applauded for singing a common sailor's chant in character – having a sort of “Sally Brown, oh, ho,” chorus; and requiring the action of pulling a rope, spitting upon the hand, and the accompaniment of a horrid yell….”
[Horace in New York, Campbell, 1826]

Forebitters are not shanties. They are forebitters and always have been. There is no maritime "work" involved. Calling them traditional work song denies the singer and the stage of their own traditions does it not?