OpenStack is big and complicated. It's composed of many moving parts, and it can be somewhat intimidating to figure out what all the bits do, what's required, what's optional, and how to put all the bits together.
In the attempt to tame this confusion, the OpenStack Technical Committee defined what's part of the Integrated Release and what's not, so that you, the consumer, know what's in and what's out. One of the unintended side effects of this was that new projects were treated as second class citizens, and had trouble getting resources, developers, and a seat at the table at the developer summit.
As OpenStack continues to grow, this became more and more of a problem.
With the Liberty cycle, the Technical Committee has taken another look at what makes a project part of OpenStack, to make things better for the projects, as well as for the consumers.