Cannot charge if powered up

I am not sure if this a bug or a feature by design.
If I boot first without plug in the USB-C power, I cannot charge if I plug the power later.
Meanwhile, if I plug in the power before power-on and booting the system, the system is being charged.

There is some information about this issue here:

I have tried 2 USB-C power adapters. One is Anker and will only start charging when the Pocket is off (and remains charging after power on). Another is a Lenovo/Thinkpad adapter that will charge the Pocket even when plugged after the computer is on.