I think this is interesting for two reasons. One, I tend to agree that, in my main feed, I want to see just what I've subscribed to, in the most to least recent order, that's it. I come in to see what's new, and am probably done after that. Two, on the chance that I want to spend more time in the app, there is a "Discover" or "Explore" tab for exactly this. The feature they're forcing into the main screen exists, but apparently doesn't drive enough views by itself.