After views went into core, the entity system continuously evolved, so for example it provided support for a unified storage for fields, which itself can and should be swapped out. These changes though did not got integrated perfectly within views, which was the main focus of the work. The list of issues have been the following:

* https://www.drupal.org/node/2371605 (can't say a lot about this issue, but basically some entity storage related API had a bug)
* https://www.drupal.org/node/2407801 ( Allow to use base fields (node title) similar to manually added fields (like the node body) in views)
* https://www.drupal.org/node/2341323 (Allow existing views configuration to adapt automatically to entity storage related changes in the database)