It's probably neither 3" or 3.2" but the 2.8" Mitsumi QD. The author of this article seems to have gotten confused with them too, because the samplers and yamaha devices used 2.8" QD's, as did the famicom, NOT the 3" CF2 disk. The confusion arises because while many manufacturers referred to QD as 2.8", some rounded and referred to it as a 3" drive.
The QD format was used by Akai, Korg, Roland and Yamaha on their early samplers (and in their midi data filers wrt Yamaha).
http://www.cpcwiki.eu/index.php/CF2_Compact_Floppy_Disc
I remember reading at the time that Alan Sugar got a job lot of the drives at a rock bottom price...