Here's another hypothetical: suppose a manager makes a practice of emailing all their male reports every week with "Just wanted to say that we appreciate your work at this company. Your work this week on ___ was fantastic," and not their female reports.
Then there is no question of cost or value or function, other than the five seconds required to figure out something the female reports worked on this week.
Would this be an acceptable thing for the manager to do?
That seems like it would be discriminatory, because the message contains no sex or gender-specific language, and sending the same message to the women would take no more time (per employee) than the men. Modifying the message to contain gender-specific language would mean that the manager would have to have two templates, but intentionally creating a gender-specific template for the purpose of excluding one group would itself be discriminatory.