Twitter has been showcasing, for a while now, Tweets that you missed while you were away. These are tweets that are popular, and from those that you follow. Often times they will be in regards to subjects that you often Tweet about. It's pretty helpful, showing you about 4-5 Tweets when you login - after being away for a few hours or longer. And now it looks like Google+ is doing the same thing, in its latest tweak to their new design.
Google+ is rolling out version 7.2 of their Android app - which this is likely part of that update that is in a staged roll out right now. Now in your notification panel, you will see a new notification at the top which tells you that you have missed posts, and who they are from. It's not clear if these posts are from people you interact with often or not, but it likely is. This isn't a big change, but users will notice it, and some may not like the change. There doesn't appear to be any way to turn this off either, like the Chrome custom tabs that are also coming in version 7.2 of the app.
The main reason that Google+ is doing this is to get users to use Google+ more, or at least spend more time using it. It's something that many social networks are trying to change these days. As Twitter and Facebook have plenty of users, but many of them aren't that active on their platforms. Something they have been attempting to change, and Google+ is also following that same path. Google+ is one of the smaller or lesser used social networks, but still very important to the search giant. Google+ recently went through a pretty big redesign - which showed everyone that its not going anywhere - and they are also updating that new redesign quite often with features that were left out or needed to be changed.
The latest Google+ update is rolling out, as of this afternoon. It's a slow staged roll out as usual, but everyone should be seeing it hitting their devices in the coming days, if you don't have it already.