It is possible that it was also reported in US forums, but it wasn’t answered yet AFAIK.
It is a not-breaking issue, but an annoying one for sure, and it is easy to reproduce. In fact, I reproduce it every time with my life style (and no, I’m not going to change it to “fix the problem”).
With macOS, every time I log in to battle.net client application and then I suspend the system (usually after some play session), battle.net considers me as logged out and cannot re-log me in. In order to fix the problem I have to restart the battle.net client. Moreover, I have to re-type my password, making the checkbox “remember my password” as useless.
While it does not prevent me from playing, re-starting the client just to play the game is sign of poor quality that I’m not used to.