But the MPF920-E is indeed a high density drive. It looks like that Aminet package is used to do a high density format with the original Amiga Tech. internal floppy drive (880KB), not a real HD drive.
The Amiga Tech A1200's shipped with high density drives, however they could only be used as 880kb drives as they don't spin at half speed when you insert a high density floppy disk.
High density disks have double the amount of space per track, so if you spin the disks at the same speed then you need to process the data at double the speed. The Amiga can't do that, so you have to slow the data down to low density speeds. Either by slowing the motor down or by reading the data into a buffer and then passing it to the Amiga at a slower speed.
Even if you had a floppy drive that would spin at half the speed, you also need to find someway of getting the motherboard to generate the correct id for a high density drive. I'm not even sure an a500/a600/a1200 can do that, on the a3000/a4000 there are jumper settings on the motherboard to do it.