[3.0.8 - Offline Captures, Account Deletion and more]

No. you can even switch off your phone without being logged off.
it's a pitty that the "sign out" button is right next to the "offline captures" button. I allready signed out a few times by mistake.

[3.0.8 - Offline Captures, Account Deletion and more]

If you log out of the game, all your offline captured positions (which are not lands yet) are deleted