It seems that since around the time of the 5.0 launch, pageviews from the iOS app are no longer being recorded correctly:
Data source:
hive (default)> SELECT year, month, day, CONCAT(year,"-",LPAD(month,2,"0"),"-",LPAD(day,2,"0")) as date, SUM(view_count) FROM wmf.pageview_hourly WHERE year = >0 AND access_method = 'mobile app' AND user_agent_map['os_family'] = 'iOS' AND agent_type = 'user' GROUP BY year, month, day ORDER BY year, month, day LIMIT 1000;
See also T130432 (an issue which was caused by the app no longer sending unique device IDs in most cases - however, one would expect that it still sends correct user agents, i.e. that the same issue does not occur here)