[Rezo]

"Not only does SAK say that the system may reduce the labor force -- for instance by tempting mothers of small children or those close to retirement to take more time off"

As long as the unemployment rate is > 0, that sounds like a net benefit for UBI. Someone else who isn't at the same life stage can then fill the freed position. You would only think this is a bad thing if you see workforce participation as the end-goal in itself, while all signs point towards massive societal upheaval due to automation without something like UBI.