For me, one of the defining features of gravy is that it's made from a roux, but I think that's just because my family always made white gravy as opposed to brown gravy (which is a base thickened with a starch slurry, as opposed to a full on roux).
I'll have to give this a try! It looks delicious!
If anyone wants a good white gravy recipe, I usually make the one included here: https://www.rabbitandwolves.com/vegan-crispy-black-pepper-cauliflower-steaks/