"Qualcomm have had under screen tech for a while too."
Clearly you didn't read this bit... UNDER SCREEN.
Qualcomm didn't have this tech "for a while" and it's definitely not ready for mass release. It's a tech demo on a trade show, not something that can be released on millions of iPhones. I know Apple is using their own version, but Qualcomm and Samsung can't get it to work under the screen reliably and fast, so it's not that strange if Apple can't either.