I still think HST is an inaccurate descrption.
I heard someone refering to HST as being just half of what we think of as a HST. And that is much more accurate. So the square is made up of two HSTs.
The squares were cut in half on the diagonal, making a right angle triangle that is half of the square. Makes a lot more sense, but I'll bet it won't catch on. That would be almost like changing the qwerty keyboard. Ain't gonna happen!