I’m on windows but had similar issues, what I think is happening is this.
Within each font is a ton of metadata with the font name, family, weight,
opentype names, and alternate names. You can see what I mean here:
View post on imgur.com
Sometimes the font creator is a bit careless about how they fill in these blanks.
If I have Meta Book, and Meta Normal, and Meta Medium… then ideally what I want
is the family name on all three fonts to say “Meta” and then the rest of the blanks
describe what flavor of Meta we’re dealing with.
But some font creators annoyingly put e.g. “Meta-Book” in the book font’s family name,
then “Meta-Medium” in the medium font’s family name, and so on.
Then it will appear as two different families within indesign and other apps.
Your operating system is sometimes smart and figures out that despite the incorrect
family naming method, these fonts all belong together.
So in the Font Book, everything looks good.
Unfortunately, the best fix I’ve found is to actually own a font editing program
(in my case, FontLab, which is available for Mac) and manually redo all the family
names so that they all match, in your case you’d want all of them to say Whitney.
It’s tedious, and probably not realistic if you don’t plan on making fonts
(fontlab is expensive).
You might be able to find a cheap or free program to edit this metadata.
Maybe DTL OTMaster? https://www.fontmaster.nl/english/OTMaster_rdrct.html
And you’ll have even more options if you use WINE or some other windows emulator
that can run windows apps on mac.