I see it as being like cuisine.
I know Italian cuisine pretty well. Not like, infinitely well, but if someone tells me they're making an Italian dish, I kinda know what to expect--even though two Italian dishes can contain almost no ingredients in common, I know the shape of it. If I'm told an Italian recipe, I can generally cook it if it doesn't require special equipment or rare goods.
I don't know French cuisine hardly at all. I've heard of herbes de Provence, for example, but I don't know what's in it. Even though French cuisine and Italian cuisine are related (after all, France borders Italy), I'd have to learn all the ins and outs, the ingredient substitutions, the intuitions for the right ratios of ingredients. But given the similarity, I might be able to wing it. Conversely, I know literally nothing about traditional, say, Senegalese cuisine, other than that it includes jollof rice, which I heard of for the first time a few days ago. I would not be able to wing it with cooking Senegalese dishes, as I know nothing about the flavors or ingredients.
I do think it is silly and excessively self-limiting to choose to never prepare any dish that doesn't come from the one country you grew up in, or the one cuisine you first practiced cooking, or whatever. I would understand why someone might choose to do that...but I would also think they are self-sabotaging, and would not feel all that much sympathy if they then complain about the limitations arising from that choice. And...if they opined things about cooking in general, I would not give those opinions much credence.