Isn't this... stupid?
Using a larger font size or a font that renders larger at the same font size means you can write less content in the same space.
Sure, it might seem stupid over something trivial as schoolwork, but consider the same situation widely exists in the real world.
You won't say it's stupid when you need to send business documents and there's money on the line if there are incompatibility issues. Suddenly Windows, Office, and Adobe make a ton of practical, industrial sense.
ca 2000 when I was in HS, it was clear that the font & format limits were to also help get students used to submitting printed standardized manuscripts later in academia.
But also to save the teachers from all of the same empty formatting flourishes which people do in the corporate world too. Colored text, unrestrained use of bold, fonts which are harder to read ...
12 pt, double spaced, Times New Roman was honestly a standard which started to be taught as early as elementary school.
In uni, strict formatting rules weren't uncommon either! At my school, within the humanities, formatting was strict to get students used to APA/Chicago and more persnickety guides.
Even in Analytical chemistry, charts made in Excel were banned outright because the prof wanted to push students onto tools capable of generating publication-ready graphics.
You could excuse not having adapted to, say, AI-assisted tools yet. The industry has to figure out best methods, then it has to trickle out so the younger instructors know about, and then it has to be propagated out to everybody, standardized, etc.
But word processors that could ignore fonts and provide word counts were pretty old tech by 2010! If you haven’t adapted your teaching to something that’s been widespread for decades… that seems like a willful ignorance.