That's pretty much sexism (or racism or ...ism) in a nutshell. Evaluating people by the statistical generalizations of a group they belong to, rather than evaluating them as individuals.

No, sexism would be treating it as a rule ("women miss work to care for their children") rather than a prior ("women have a higher probability of missing work to care for children").

If they are asking the question, they are attempting to evaluate the person based on their individual characteristics (i.e. their answer).

Some research says black people are Nx more likely to commit property crimes than white people. By your logic, it's not racist to ask about someone's race in an interview, because you might just be reasoning the likelihood of them stealing office supplies.