It appears like this is a bug with the PWM feature of the LED library from the connectivity framework. I will report it to the SW team so hopefully it gets fixed in future releases of the SDK.
The BOARD_InitRGB() is called BOARD_InitLEDs() in the QN9080 SDK and PWM_StartEdgeAlignedLowTrue() is not available for the CTimer module used by the QN9080.
As a workaround you can generate PWM signals by using the CTimer driver as in the CTimer Simple PWM example located in the driver_examples folder in the SDK.
Let me know if you have any question.