P2425DE - Direct Keys - Expected Behaviour?

I've just purchased a P2425DE monitor.  Daisy-chained off via the DP out is an older P2412D.

USB-C input - Dell Latitude

HDMI - Desktop PC

Via the P2425DE OSD, I've configured two Direct Keys to allow me to swap between the two inputs via the joystick.

Direct Key 1 - Off

Direct Key 2 (right) - Input : HDMI

Direct Key 3 - Off

Direct Key 4 (left) - Input: USB-C

Right now, the monitor is working from the the HDMI input.  If I click the joystick to the left, it switches to USB-C as expected.   I don't have my laptop physically connected at the moment, so there is no video source on USB-C which the monitor reports.

If I then click the joystick to the right, rather than jumping to HDMI (as per the DK setting), it brings up the Shortcut Menu, so I have to click into Input Sources and then move to HDMI.

Is this expected behaviour?  Why doesn't the Direct Key 2 switch to HDMI regardless of the signal status on other ports?  My hope with configuring the Direct Keys in this way was to have a single click to move between USB-C and HDMI inputs (without having to navigate any menus).

Thanks!