https://bugzilla.redhat.com/show_bug.cgi?id=851758
--- Comment #5 from Cheng-Chia Tseng pswo10680@gmail.com --- Sorry, I don't know ibus have that behavior. :P
The description in preference does not mention the behavior that ibus is going to remember the engine state from last session. I think this behavior is confusing some users like me.
If this is not a bug, I think that it is better to make it clear in the box. Or to make it match the behavior - default one is always the one you use since login, as people's understanding from the description reading.