The "pre-schooler" term and its definition are loaded with location-sensitive information. In some countries, pre-schooler would mean under 3 yo and not older than 3 yo.
It gets quickly confusing as many culture have different definitions of school periods (kindergarten, pre-school, nursery, middle school, elementary school, college, university, high-school, etc...), and while we can of course argue that we communicate here in English, it might be a bit too demanding that people from other background also know and understand the definitions of these terms in an English-speaking or more global context (and it may even vary between English-speaking cultures).
That can also creep in in other tags of course, but that was the one that struck me today. For instance, to a lesser level, "infant" can be a bit tricky for French-speakers as it's a "faux-ami" of "enfant" (which means "child", not "infant").