Thank you so much for letting us know about this, especially as this is a spankin' new addition to the feature and want to know about your experiences with it 👍
An immediate reaction would be to believe this is a bug, but it is actually a matter of an implementation detail.
The way the auto logout feature works is that the session expiration countdown begins when you leave your monetary account overview (for example) and start browsing the Together posts.
We have notified our dream team so that they can look into this. Cheers! 🌈