The Apple II series could power many more external drives than any compact Mac model could. You could easily put 3 external floppies on most Apple IIs, but you couldn't do that on the Mac. I assume therefore that the Apple II has a higher floppy drive output current. In such a case, I would assume that you might damage your compact Mac by trying to power this hard drive from the Mac's floppy port.
Even so, the seller mentions that the lady who previous owned this drive messed up the power plug. Since sellers tend to play down problems (in order to make a higher profit sale), I would assume the connector problem is much worse than the seller is making it out to be. I personally would not buy it for that reason alone. But it might be a fun drive for those who like to tinker and fix busted connectors.
The real interesting part of this item though is its size, which is why Mac128 brought it to our attention. I think the compact size would be most practical when using a Mac 512ke or Plus, where you already have an external 800k floppy drive and you could then add a SCSI drive without having to figure out where to put it. But for my SE/30, this sort of drive is actually rather bothersome. The SE and SE/30 were built to accommodate an internal HD to get it out of your way. And if you don't like that, you can get a zero footprint drive to mount under the SE or SE/30 -- which also gets the drive out of your way. Since most SE and SE/30 owners don't use external floppies, there's no real benefit for owners of those machines to have an external drive that is the size of an external floppy. This unique hard disk is therefore made for someone who has lots of similarly sized drives -- it makes it convenient to stack them.