I've always wondered why they can't just build a fingerprint sensor into a capacitive touchscreen. After all, a fingerprint sensor IS just a really high density

I've always wondered why they can't just build a fingerprint sensor into a capacitive touchscreen. After all, a fingerprint sensor IS just a really high density capacitive touch sensor right? Or is that not right? Google gives me no answers and I assumed it was not fundamentally impossible, just that it was two separate companies with two separate production lines making touchscreens and fingerprint sensors so it was hard in practice due to the realities of supply chains. Many existing fingerprint sensors, like TouchID, were glass, and I wonder why they can't just make it bigger and put an OLED under that glass (even if it was only dense enough for fingerprints at one spot). Yet here we are, 4 years after the downgrade too FaceID, and still not a single phone in existence with a capacitive fingerprint sensor in the screen. Am I wrong about the technology or what?