The person who worked on the 32bit floppy driver for Windows 95 studied the specifications in quite some detail, and he realised that by issuing just the right sequence of commands, you could determine if there was a floppy in the drive without spinning it up. There was just one problem: floppy drive manufacturers implemented two different styles that were each other's exact opposites: if the sequence of commands on a drive with style "a" would return a "1" if a floppy was present, drives with style "b" would return a "0".
Within these two styles, results were 100% reliable, but the difficulty was, of course, to find out what style the drive in the computer actually used. Microsoft came up with the idea of using an additional "training" step during setup, in which a user would be asked to inset a floppy into the drive, so that the setup routine could issue the sequence of commands and find out what style the drive used.
This method was deemed too troublesome for a number of reasons. The biggest problem was that most users would eventually buy a machine with Windows 95 pre-installed, and Microsoft didn't trust OEMs to perform the training, mostly because OEMs change suppliers all the time.
Another option was to simply test the sequence of commands without a floppy in the drive, but Microsoft figured that users would freak out over their floppy drives going berserk for no apparent reason. "Thank you for using Windows 95. Before we begin, I'm going to turn on your floppy drive light and make grinding noises. Press OK." I can see how that would, well, suck.
Still, it's an interesting little feature that didn't make the cut into Windows 95 (or subsequent versions).