Okay, fine. You can taste a tiny difference, but mostly in the texture. The cornstarch version is slightly more sturdy than real cake flour. It’s like the difference between a cashmere sweater and a really soft cotton one.
Will anyone throw a fork down in disgust? Absolutely not. Unless they’re a pastry chef with a magnifying glass. And if they are, why are they at your house?
Plus, you get to feel like a kitchen magician. “Oh, this cake? I used a top-secret flour hack.” You’ll get oohs and ahhs.