I wouldn't go as far as say they're incompatible; I'm sure it's doable. But there's a pretty big difference in believability between the claim that "engineers are much more likely to be FIRE people, to the extent it makes a noticeable difference in the engineering job market, now of all times" vs "FIRE people w/ kids exist, but are outliers among outliers"
Ok, that seems reasonable. I got stuck on "there's plenty of engineers who have kids (hence, very much not FIRE)," which seems like an oversimplification of your views.
