I had noticed that the drive was acting strangely. Firstly, it doesn't click when empty. Secondly, if I boot using a Workbench disk then remove the disk, the drive starts clicking like mad, the floppy light comes on and a DF0:NDOS icon appears on the Workbench. If I put another disk in, it reads it and this weird activity stops.
Seems like it thinks that the disk/floppy is still inserted even when the drive is empty. There is a button or what you call it that is pressed down when a floppy is inserted.
See if this button is stuck or something.
Or as you said, the drive might infact be a pc/mac floppy without this function.