Regarding documentation at https://ds_infolib.hcltechsw.com/ldd/lcwiki.nsf/dx/IBM_Connections_4.0_Metrics_Frequently_Asked_Questions
... Read events originate from Connections Mobile App are currently NOT tracked by Metrics (limitation confirmed by L3 support).
Create, Update, Delete (CUD) events originated from Connections Mobile App are already tracked by Metrics.
Now, for tracking of read events, Connections Metrics provides the Read Event Tracker API: https://ds_infolib.hcltechsw.com/ldd/lcwiki.nsf/dx/Metrics_Read_Event_Tracker_API_ic60
Looks like that Connections Mobile App needs to be enhanced to make use of this API.