Let's take windmill like in the example, it has 3 blades, each maybe at most 5 degrees wide (out of the 360 for a circle). So that covers 15 total degrees or 1/24th the wind area, so at absolute best, it's about 4% of the wind power in that area being stopped. But the blades don't actually capture 100% of the wind power, a good amount will deflect off, those blades are not 5 degrees wide, they're less and they aren't straight blades, so again they capture less. Further the blade only captures a small vertical section of its own footprint, so it captures dramatically less wind power. Lastly blades are spaced with a good amount of clearance from each other leading to even less wind power captured. In aggregate, even by entirely layman measure, these likely have an immeasurable impact on another wind farm.

I'd bet if you built a mile high, mile wide wind capture device that captured 100% of wind power going to it, and then put a 2nd one 1 mile directly behind that, you could just maybe get a few % measurable impact.

it does make sense to me too. the effect is just not "big", whatever that means xD.