Our emails contain buttons w/ universal links behind them. Doing a preview (peek) shows the results of sending the link to Mobile Safari. Normally when the button is pressed (or pressing further into the peek--that is, doing a pop) the link is sent to our app.
The page rendered by Mobile Safari may/will look different than what the app shows. So the transition from the peek to the pop can be very confusing to the user. This doesn't seem like correct behavior, although I don't know how the peek preview could be handled otherwise.
Filed as bug #22870643.