Why does the screen time out cancel screen orientation?

[Android Central Question]

I use my phone to study videos. This means I'm often pausing videos for a while while taking notes. The screen times out and when I unlock it portrait mode has gone and it takes a moment of phone juggling to activate it. I don't want the screen to stay active longer so as not to waste battery. My old Xperia Z2 didn't do this. How can I change this?

I have tried apps that lock portrait mode and that is still uncomfortable as I have to activate and deactivate regularly.

To reiterate; how can I maintain screen orientation after the screen times out?

I have a Huawei mate 10 Pro without root.

 

[Sam_Gs7]

Don't know about a different method, except to use one lock
orientation Mode app mentioned by yourself. Phones after
get turned off or timeout return to vertical orientation