Yes, "dd" is fine for making 1.44MB floppy images to work with SWIM-based Macs. (Lately I've regretted getting rid of my Quadra 650; between the SuperDrive and the Ethernet port data exchange was cake with that box.) I was kickin' that old-school back in 2003-ish. (I was "dd-ing" disks on a Linux box, not OS X, but it's exactly the same thing.)
It might be an interesting experiment to see if a real Mac accepts an HFS filesystem on a 720k floppy. As I said, there's no good reason I can think of to make such a thing on a real Mac but I suppose if you have a pile of 720k disks lying around and want to use them to directly sneakernet files from your emulator setup you could see what happens.
It might be an interesting experiment to see if a real Mac accepts an HFS filesystem on a 720k floppy. As I said, there's no good reason I can think of to make such a thing on a real Mac but I suppose if you have a pile of 720k disks lying around and want to use them to directly sneakernet files from your emulator setup you could see what happens.