“More efficient” in that study just means eat less food, drink less water, need less oxygen and create less waste because women tend to be physically smaller than men. Which is so obvious it was a waste of money to even do the study.
Of course, there is a lot of overlap between the body sizes of the two sexes. I would think the only outcome of this would be to have a maximum height and maximum body weight to be an astronaut if resources are going to be an issue for a longer interplanetary voyage like to Mars rather than banning half the population for having XY chromosomes.
(You could do the exact same study comparing East Asian vs Black African astronauts btw and similarly conclude all crews should be East Asian people due to population body size averages. So not only can a scientist engineer a sexist result like in the above study, a racist one can be easily engineered as well).