I think the issue with this argument is its difficult/impossible to prove one way or the other. Not enough information is known on either side to make actual conclusions. there are certainly some cases where it does improve the lot of the workers. there are also certainly cases where it hurts the lot of the workers. and if you are only looking at the workers its easy to miss the collateral damage done.
at best its a case of gentrification, and at worst its the modern equivalent of indentured servitude.
but even at the best it has some draw backs. removing workers from the local economy to a factory that is for export only, means there is less work force in the area. less local work in most of these countries means less food production, and smaller cottage industries that the community relies on. So you have cut supply, while also increasing the amount of money available on the demand side. that disrupts local economies.
a lot of the "benefits" aren't nearly as universal as we would like to assume. Great example is all the work China does to improve a nation's economy, they are adding 500km of road, 200km of rails, a new international airport, and sea port. What they don't tell you is that no local roads connect to that new network, and actually local road use now takes longer because the new highway cut the existing local roads. the rail only runs from the port to factory, the airport only goes back to one city in China, and only Chinese ships can use the port. Its similar with any of these factories. "There wasn't electricity in the area before but we have built a new power plant...that only serves the factory. and the waste from that plant kills off 1/4 of the local food production while damaging local water supplies even more"