Its a minefield.
When the same shanty exists under diferent names, when diferent shanties exist under the same name, when there are so many versions of the same shanty, when the words of one shanty are used for the verses of another.
And dont get me started on adapting, say, a halyard shanty for use at the capstan etc.
You get 'foreigners' misinterpretations and folkies 'cleaning up' to make them sound better.
Its a minefield.