Issue seems to be related to GPU scaling which is not possible through Hyper V GPU P, but I found an obscure solution that will work for anybody. I'll leave this message for anybody who's going down the same rabbit hole as I did.
If you encounter unscalable VX Ace full screen black bar and you're using Hyper V VM with GPU pass through, you have to go to this old ass japanese website
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. Download Sandblast. Go here
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and find
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and install that.
Sandblast will scale anything however you want. It's more like a good magnifying glass that works fast. Apparantly the japanese already had this figured out.
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also works but is the older solution and slower.
These are the best solutions I found after desperate digging. I'm hoping Cunningham's Law apply here and somebody will step out and give me an even better solution.