That implies that other kinds of landholding did not have access to cheap labor - but serf, sharecroppers, and farm hands are all pretty cheap under the right circumstances.
More pertinently, the "expensive" farm workers of the industrializing countries weren't expensive enough for farming to be mechanized until the 20th century. Second half of that before it had replaced manual forms of farming entirely. Farming itself never was the driver for industrialization, but a rather late profiteer of it. It follows that farm slaves couldn't have been the blocker for industrialization, at least not as directly as you assume.
More pertinently, the "expensive" farm workers of the industrializing countries weren't expensive enough for farming to be mechanized until the 20th century. Second half of that before it had replaced manual forms of farming entirely. Farming itself never was the driver for industrialization, but a rather late profiteer of it. It follows that farm slaves couldn't have been the blocker for industrialization, at least not as directly as you assume.