[T]here was a type of employee at the beginning of the Industrial Revolution whose job and livelihood largely vanished in the early twentieth century. This was the horse. The population of working horses actually peaked in England long after the Industrial Revolution, in 1901, when 3.25 million were at work. Though they had been replaced by rail for long-distance haulage and by steam engines for driving machinery, they still plowed fields, hauled wagons and carriages short distances, pulled boats on the canals, toiled in the pits, and carried armies into battle. But the arrival of the internal combustion engine in the late nineteenth century rapidly displaced these workers, so that by 1924 there were fewer than two million. There was always a wage at which all these horses could have remained employed. But that wage was so low that it did not pay for their feed.

-- Greg Clark, A Farewell to Alms

The "Lump of Work fallacy" does seem to be a fallacy. However, that didn't help the horse. Why is that? The invention of "Artificial General Muscles" in the form of the internal combustion engine was a better-than-perfect replacement for all forms of horse labour. We should expect artificial general intelligence technology to do much the same to humans. There is no law in economics that prevents human wages from declining below subsistence. And a perfect substitute for human labour that requires no wages and is more intelligent would certainly vastly lower the value of human labour.