It doesn't surprise me. Women are generally more likely to follow safety protocols. For example, they are more likely to wear seatbelts and ensure every passenger does the same. It is most likely related to risk taking, which is one trait where there is a statistically significant difference between men and women: women are more risk averse.

Socialization largely most likely. Look at the stereotype of boys being interested in touching crawling,slimy, and gross things while girls are repelled by it. For better or worse the susceptibility to that sort of revulsion would be linked to more handwashing.

thought the same thing - men not washing hands after nookie? And whats this about sinks being too short? Distractingly crappy data categories.

It's probably a BS toxic-masculinity thing - "Only weak men need to wash their hands". I know that toxic masculinity is a controversial topic but I've met lots of folks who think this way and it is such a silly philosophical stance to take.