I think you're overstating this. The "handshake" is purely 2 simple resistors correctly installed. The problem is a lot of folks do it wrong for various reasons

I think you're overstating this. The "handshake" is purely 2 simple resistors correctly installed. The problem is a lot of folks do it wrong for various reasons, most likely never testing with anything more than type a to type c cables. https://people.kernel.org/bleung/how-to-design-a-proper-usb-c-power-sink-hint-not-the-way-raspberry-pi-4 https://people.kernel.org/bleung/how-to-design-a-proper-usb-...