The Historic Environment Scotland report, here, states that some larger rocks can be found on the southwestern margins of the cairn, suggesting this is a kerb cairn. However, the HES report makes no attempt to age it, describing it simply as "prehistoric". The report states that the monument is of national importance, "for its potential contribution to an understanding of prehistoric burial practices and ritual beliefs."
The siting of the cairn right next to the 'port of the ship' yet away from any good agricultural land, suggests that there's a close connection between whoever is buried under it and the sea; and I haven't been able to find out why it's called 'Ben Hiant House cairn'.
Map courtesy Pastmap, here.