We set logicalDPI based on DisplayMetrics.scaledDensity which we get from Android (as described in
QTBUG-29674). This affects how fonts with a certain point size will be displayed. Currently we have chosen a scaling factor that makes unmodified desktop apps look sensible.
On iOS, on the other hand, Apple specifies a logical DPI of 72, which means that a font that looks sensible on the desktop will be very small on an iOS device. This means that apps need to use different point sizes on iOS and Android.
We probably need to re-evaluate this decision. At least we need a convenient and well-documented way to create apps that work on both iOS and Android.