Are you sure it was an Irish plantation owner? Most of the time Irish people in the Caribbean were working on plantations, not owning them. From what I’ve read, the person in question was a British person from Antrim - which is on the island of Ireland, but is part of the UK and was itself “plantationed” by Britain.
It would be weird for example to refer to George Orwell as Indian, Louis Theroux as Singaporean or Duke Wellington as Irish - after all, “being born in a stable does not make one a horse” as the Duke put it when ‘accused’ of being Irish.