Will they be banned from sale in the EU because of the phone charger mandate or did that not actually pass into law? Or is there something about backwards compatibility through USBC that’s bypassing it?
USB4 is the specification for the cable, USB-C is the connector at the end. We'll presumably start to see USB4 cables with USB-C connectors to replace the current 'best' USB3 cables with USB-C connectors.
The "ban" is about connector type, not the wire itself. And it doesn't "ban" anything - as long as you can connect your device using that one type of cable you had in your drawers for five years - it is okay. That is not a "ban", just a minimal requirement. (Kinda like EU doesn't ban some type of doors at buildings - it only requires that doors could open and wouldn't be in the way in case of emergency.)