Cool until you realise Grandma is senile and can't actually think beyond piecing together text they've seen before into what they think is a coherent response.
Those keys will absolutely not work, either because they've already been used and were scraped from training data, or they are fake keys generated based on said training data.
And of course, on the small chance that they did work - I would expect Microsoft to revoke those keys fairly quickly if they start getting a ton of usage.
I tried it myself and looked the keys up. It gives you generic keys. They will work and let you install Windows, but they aren't "valid" keys so to speak. At the same time, they aren't "fake" either