I've noticed this in almost all version of Collector including the latest.
I add a cached map service to a web map and enable pop-ups on it. The cached map service has the option checked to download 10,000 cache tiles. On the web map the popups work as expected.
Viewing the map in Collector while online, the pop-ups continue to work as expected.
But, as soon as the map is downloaded and taken offline on Collector, pop-ups no longer are displayed in Collector.
Is this expected behavior or am I doing something wrong?