which never should have been a thing, because it was obviously wrong

yes AIs is more likely to use em-dash, but that is just one, by itself very insufficient, indicator.

it's like hip size. In average over the populations they are wider for woman. But the effect is too small to classify the gender of a hip bone by it's size. (Like for a specific age range and ethnicity, the difference in median is like 1" or so, while there is a >10" difference between 5%-percentile and 95%-percentile. Varying by gender in difference and exact distribution.) Well I guess em-dash are more an indication for AI then hip size for gender... lol