Gray foxes are not from the Vulpes genus, which we call 'true' foxes, and are illustrated in the post. Theyre from the genus Urocyon! Which actually evolutionary predates Vulpes. Gray foxes not being part of Vulpes does not mean they are not foxes in the scientific sense, but in the sense of it being an animal which behaves, looks like a fox, so we still call them foxes.
Also think about the crab-eating fox (cerdocyon), bat-eared fox (otocyon) and all south American foxes (lycalopex). Theyre not true foxes as theyre not vulpes, but theyre still what we call foxes! :3
See also:
https://en.wikipedia.org/wiki/Caninae