I think we did not really estimate here, there is just intuition. I made these estimates before for electric bikes vs human powered, and found that, somewhat counterintuitively, electric bikes may quickly become less carbon-consuming.
I do not accept the idea that brooming comes for free. If you add 15 min moderate activity of brooming per day, you may spend, say, 100kcal. If you add it to your daily routine, you need to compensate with food or loose weight. Energy balance in humans is tricky, which is one of the reasons people find it hard to control their weight. But things like replacing a 15min couch sitting with brooming make a difference for weight. Because they consume energy. Or do you continue to propose that replacing the couch sitting with brooming has zero energy and diet difference activity, is “basically free”? To be clear.
Vacuums help to save time. Carbon impact of vacuums and replacing human-powered activities with solar-electricity-powered ones is not especially studied. Which is why I think intuitive understanding here is lacking. Someone should develop it, maybe write a blog post or a paper.
This is not imaginary, growing replacement of human work at scale has a real impact on carbon consumption. My point is that in some cases, e.g. with electric bikes or vacuum cleaners, human power, even plant-supported, can be more vastful.