Observed behavior:

This is using app version 3.5.2.

When you log in as a user to your Moodle site using the Moodle app, the "Last access to course" column on a the Participant pages of any course the user is enrolled in updates and shows as having accessed the course.  Specifically, this is happening when all you do is login and not go to courses or access any courses via the app.  In contrast to what the "Last access" value shows in the course page, if you go to any of the course logs, those logs show that the user never accessed the course.  

• View of Participants page "Last access" field: https://www.screencast.com/t/nXImIBHB
• View of course logs showing no record for test user: https://www.screencast.com/t/4rOxWnGPB9w
• View of site logs showing Web service function called activity: https://www.screencast.com/t/drgiTL0x4BD 

Expected behavior:

I believe that if there is no logged activity in a course, then the "Last access to course" field should reflect that. This could cause confusion for teachers that use that field at a glance to see if users have accessed their course.