Not necessarily. Slavery might have indirectly assisted the north's industrialization in at least a couple ways. (1) Accumulation of financial capital in the hands of an investment class (2) Cheap cotton gave northern factories a competitive advantage.
That is a good point although there should also be a way to compare and contrast with other countries that didn't have slavery as an "advantage". Then you could try to back-apply the model to other countries, like if the English outright owned the Irish then economic growth would have increased ... or would it have?
