Note that I'm considering the triangular trade as a form of colonization; even if it didn't involve proconsuls, it involved an external actor explicitly fomenting a hierarchical and extractive social order.

If you redefine colonization, you can get the results you wish.

Note that here homunq's stipulation actually makes his claim more false. After all the parts of Africa benefiting from the triangle trade were some of the richest and most well off parts of Africa (not for the Africans being sold obviously) before colonization proper started.