@c-attack haven't bothered to properly test, however it appears to follow the same pattern: if iCUE closes gracefully then Hardware Lighting is instantaneous, if it freezes up when the computer shuts down then the lighting effects freeze until it times out, then the LEDs fall back to Hardware Lighting (I assume - by the time the lights default, the PC is done with shutdown).
I have noticed that when iCUE isn't gracefully closed as part of the Shut Down flow, the LED strips connected to Channel 1 of the Lighting Node Pro default to Solid Red for shutdown rather than the Hardware settings set in iCUE