I blame Walt Disney to some extent for the popular sailor/concertina connection.
I know I may have been affected (infected?😁) to a small extent by the leading man sort of playing one in one of the Jules Vern remakes Disney did in the '50s.
I think the word 'shanty' has come to apply to most sea music, much as the term 'classic' now applies to most automobiles more than a few years old. The language seems to morph and I suppose it always has.
The instrument (any flavor, duet, anglo or english) seems to suit the sea music genre, it depends on the player not the instrument to interpret it.
Its all good.