The CMS can and does apply it's own updates to the base Joomla
Platform. The platform doesn't control the CMS and the CMS is welcome
to make it's own additions as it feels. The CMS does push back some of
those changes but that doesn't necessarily mean they are included or
aren't further changed.
In this particular case it's an unmergeable pull request:
https://github.com/joomla/joomla-platform/pull/1261
Cheers,
Sam Moffatt
http://pasamio.id.au