Maybe they mean "when using the metric system as an American"...

It is highly language dependent.

In Germany you will sometimes see Qm for "Quadratmeter" (m²).

Mostly in lowercase, especially when talking about apartments or houses

Same in Italy, mq.

I have seen usage of kvm (kvadratmeter) in Sweden

Like we need another overload of "kvm"

(Kernel Virtual Machine in Linux or Keyboard Video Monitor in server switching kit)

sqm instead of m^2 is also just a way of typing it on a mobile keyboard.

I’m more used to seeing “m2” on mobile, but it’s probably different between regions.

More people seem to find the ² on mobile keyboards than they do on desktop keyboards. It's still rather uncommon, though.

If anything, I would've expected phone keyboards to turn m2 into m².

A gr (grain) is an antiquated measurement apothecaries used