Power management on any Android phone is at the discretion of the OEM. It’s one of the reasons why major Android releases take time to be made available for a particular model phone, or might never be made available at all. On many phones running Android 7.0+, the “restricted battery usage” setting will have no effect, because the phone’s OEM chose not to implement it. For devs to try to assert this to be the immediate solution to the problem is as nonsensical as having removed the QUIT button to begin with.
I am using an LG G7 ThinQ, and on my otherwise-idle phone, the battery will deplete at approx. 15%/hour with the GoW client in the background, and the only way for me to prevent that is to force-close the client.