How could Lois automatically know what he would / wouldn't be good at, anyway?
And in that same season when Jessica asks her how she knew about the "gay" thing, Lois goes "sweetie, I'm a mother" - how does that make any difference?
it is common in sitcoms for moms to seem like they know everything, and Malcolm in the Middle exaggerates this a lot, since Lois keeps outsmarting Malcolm. It is just funny, no need to analyze it further, lol.