Maybe, but it may not be a huge issue. I've had very good luck using apps split-screen in Android 7.0, which has a similar aspect ratio to classic BB devices.
Good point. I was going to disagree with you, but then I tested some apps just to make sure. I'm actually surprised how much stuff works with split-screen. I have apps that I use once in a blue moon, for example the Avianca app, and it works despite throwing the "this app may not work with split-screen" notification. Same for Spotify.