The criterion that Apple makes use of for the “Design Model” property in “Sensible Collections” is undocumented.
Nonetheless, it is seemingly to make use of the PANOSE knowledge within the font, which is used precisely to explain the visible traits of the typeface.
From a fast have a look at your font, the PANOSE knowledge is ready to “Regular irregular”, relatively than the anticipated “Monospaced”.
So that could be the reason for it.
Nonetheless, I’ve had issues getting my very own (designed) fonts to look within the “English” assortment in Fontbook; however following a OS set up and reboot, they’re now displaying. So it might be a font cache that wants clearing, or only a reboot.