How is then law enforcement getting what they need from people's iphones? Because I understand they do, in some way. And I'm not asking about forcing people to hand over pin or fingerprints, but just by themselves.

Lockdown Mode is focused on reducing the attack surface from Safari including the WebView and Apple services including iMessage/FaceTime. It does nearly nothing to protect against non-browser/non-messaging attack vectors in the OS or other apps. It's up to app developers to implement similar restricted modes and also baseline exploit protections. App developers need to explicitly opt-in to using the standard exploit protections used in many parts of the OS and Apple discourages doing it:

https://developer.apple.com/documentation/Xcode/enabling-enh...

Here is one example how: https://news.ycombinator.com/item?id=47716490