The end values and framing of the topic matters a lot. His end values are governance and socio-economic indicators as defined and measured by World Bank and the like, which is perfectly scientific as far as economics and economic history goes. His framing is "colonial legitimation", i.e. the more natives become employed by the colonial institutions and receive its services such as healthcare and education, the more it counts as (legitimate) colonialism, whereas mere slave trade will not count as colonialism insofar as slave traders are mobile between trade posts and do not govern a colony.Unfortunately I can't remember who wrote it (perhaps the minister of colonies?), but as I said that was almost exactly the argument for why Indonesia shouldn't be independent.
Incidentally, the former colony learned how to be invited as a colonial power: https://en.wikipedia.org/wiki/Act_of_Free_Choice