Any documentation of this new settings: mobile_session_timeout_minutes

I've observed that the session key that my code generated with /restapi/vc/authentication/sessions/login using explicit username and password became expired after 30 mins. The community is having browser's session inactivity timeout set at 90min. Then I scanned the community level settings and found this mobile_session_timeout_minutes setting with a value of 30. This seems to match my observation. I was looking for any documentation for this settings, and trying to find the page within community admin to set that value. All I could find is this post, in which seemingly misinformation is provided.

Is there any documentation available for this? and explanation on the impact. We have heavy customization that utilize self-generated session key to operate. If the session key expires unexpectedly, bad things are expected to happen.