The Jarawan Bantu languages form a closely related cluster, stretching from Northern Cameroun, into Adamawa and across into Plateau and Bauchi
They are very closely related to Bantu, indeed to the A60 languages and they have only not been treated as Bantu because their nominal prefixes are now frozen possibly due to contact with Chadic.
However, on lexical grounds they should be treated as Bantu proper. Their exclusion is typological rather than genetic
But of course this does not explain the motivation for their extraordinary migrations..