I do wonder if this is an issue with USB4/TB4 docks in general on the FW16 and not just CalDigit. Maybe someone with an eGPU dock or similar that uses actual USB4 could give it a test, like in your case an extra display from one of the USB4 ports on the TS4. USB and DP ports work fine even when its not detected as a USB4 hub because I assume those use regular USB and DP-Alt Mode.