As pointed out in another answer, you are getting Git checkouts due to the `"preferred-install": "source"` in your composer.json. You could remove that (or replace the "source" value with "dist", although presumably you have that there for a reason. 

To solve this problem, there is a module called [Composer Deploy][1], that will augment Drupal's internal version information with information from composer's metadata. If you want to install both from source *and* you want version information, this is the way to do it.


  [1]: https://www.drupal.org/project/composer_deploy