The way that loading it crosswise causes it to shift into a double half hitch, turning from a "hold fast" knot to a slipknot... That's funky behavior and should disqualify it from being among the first few knots people learn. If you're using it for its advertised purpose, it's downright dangerous, and the square/granny confusion is just needless pain to discourage a newbie.
If you wanna tie two ropes together and have a less finicky experience, use a fisherman's knot. Which is basically a pair of overhands, each around the other rope.
It's a much more reliable knot for trying two ropes together, lacks the annoying gotchas of the square knot, and for a long list of reasons I won't bore you with here it is a better foundation for learning other knots. (It's no good for drawstrings though, too reliable, no quick release).
Reefing a sail or tying a parcel, a reef knot the role will fulfill. But joining two ends one should only use bends, And a reef knot's a sure way to kill.
⸻Stuart Grainger, ex-Master Mariner, 1985. Referenced from "The Complete Book of Knots" by Geoffrey Budworth.
But since modern sailboats don't require knots for reefing, and modern parcels don't require tying, I think the use cases for a square knot are now pretty narrow.
Some times I use them to finish off some lashing because they can be easily tied while keeping tension, but that's about it. It's just not qualified for to be the first knot we teach a tenderfoot.