Being able to produce more is not the same statement as getting richer. Nor is having higher productivity the same statement as getting richer.
I’ll agree entirely that historically these three have been closely aligned. But they’re not the root cause.
Getting richer means being able to consume more. Nowt else either. So if our African farmer is able to consume more in the coming century then our African farmer is getting richer in this coming century. Which could indeed happen through the industrialisation of that continent. Or through us finally reaching true communism, where we have dealt with the scarcity problem in goods (non-positional goods, obviously) and the African farmer is able to consume more.
As with the skinning of cats there is more than one way to reach our goal. Making everything cheaper will make all richer just as well as employing people to make things will.