That is expected behavior. The tabs each run their own history queue, so leaving one tab and then coming back should keep the user where they left off at in that tab. It actually allows for better expected behavior in my apps, as it allows someone to go to a different tab when in the middle of doing something, and then come back without losing their place. And it helps that the back button is still there when needed when their on that detail page.
I’m not aware of a config option in Ionic that will reset the tab history when you leave a tab, but there might be. You could also manipulate the history in your controller, probably with a
$stateChanceSuccess listener, that could reset the history on that tab when you detect that someone is leaving your “Chats” tab.