I mean, I would call looking at another team's art of Owls and deciding to implement that in your own D&D project largely a coincidence. It makes a lot of sense to me that the D&D team is working on stuff for the Feywild, and decides to add more racial features. Then while their brainstorming Fey races to add, someone comments "Hey the MTG folks have a lot of Owlfolk art hanging, maybe I can use that as an idea!"
Another point I'll make, is that by the stories I read, the Dragonsguard are really more "wizard police officers" than either of the ranger/monk subclasses in the UA. It could make sense as a wizard/sorcerer subclass, but monk/ranger seem like bigger leaps to me.
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Also, I took a look at the MTG wiki to see if there were other races that could fit in the UA Fey, with swapped names.
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Arcavios
There are a ton of races here; and although I could swap some of these into the Fey UA, such as Frog-folk instead of Rabbit-folk, or Arcavios Orcs instead of Feywild Hobgoblins, or even Dryads instead of Fairy... there a lot of races here that aren't in the UA that seem like they should be included in a Strixhaven setting. There is a prominent Efreeti character in the stories shared, and a Vampire as well. Djinni, bearfolk, and kor are also prominent omissions that are also in other MTG settings.
Anyway, this all leads me back to my thoughts that these are more coincidences than anything more serious. Obviously I could be wrong, but there are a lot of inconsistencies in the Strixhaven theory, and I'm leaning towards some other largely unhinted at product.