Sorry but this is not a bug, Time in Unreal Engine has different usages on different contexts, specially when also considering client/server, simulation start/application start, networkign and so on… 
I explained a with a little more details on this other topic:
I agree that we should have more control over time within our code and applications, but, these aspects would be a feature request for new functionality and not a bug report, since what you said about the already existing functionality is not a bug at all and already working correctly…