First, I do not use a Microsoft account on MY PC.
In your initial question, you said that you have a "Fully verified Microsoft account". This means that you use a Microsoft account with your PC.
Second, I NEVER enabled Hello, or set a 4 passkey.
Also, if you setup a PIN, you're using Windows Hello. Windows Hello is just the "umbrella term" that houses a PIN, Face recognition (Face ID) and Fingerprint, as well as a security key. You can't use Windows Hello without a Microsoft Account. I thought maybe you use your Windows Hello sign-in method to sign in to your apps (which is a passkey), but I guess not.
SO, why is the STUPID MS "security" doing that?
I gave you a reason why it could be happening, because you only said "I frequently experience a Pop up titles Windows Security Making Sute It's You, on my home computer, inside my home. It requires me to type my 4-digit PIN." There wasn't any context that I could go off of, which is why even Emily said "That's really the scenario I can think of that could prompt such a thing." But if that wasn't right, I'd try to find another solution for you.
If you don't know, do not invent a response.
Finally, without proper evidence and explanation (e.g. pictures, error messages, etc.), I only have so much to go off of to help you, so I can't really not "invent a response" when you've actively sought help in a public community where anybody from anywhere around the world can post on any question to give answers.