Yeah - this suggests the simple explanation is true, if you reduce the incentive to work then people work less.

There is a lot of speculation that that's not the case, but it doesn't seem to really hold up.

This comes up a lot in lefty politics imo - similar to people arguing (erroneously) that increasing housing supply raises rents or reducing crime enforcement reduces crime. The simpler/dumber causality around incentives seems more true in all of these cases, the complicated second order theories fail to hold up.