Recent versions of the iOS app use sections=all instead of sections=0. Our string does not reflect that - https://github.com/wikimedia/analytics-refinery-source/blob/master/refinery-core/src/main/java/org/wikimedia/analytics/refinery/core/Pageview.java#L131 and so pageviews from iOS app installs will be undercounted.
the resolution is to turn that into a regex of sections=(0|all).