This doesn't make sense. Google+ Photos had a different policy: "Only photos over 2048x2048 pixels and videos longer than 15 minutes count toward your storage limit." Google+ even had a setting that resized your photos to 2048x2048 or less, so they stayed under the free storage limit.
Google's new policy doesn't seem fair to those who pick the "original" option. If you upload photos that are 16 MP or less or videos that are 1080p or less, you should be able to store them for free, regardless of the Google Photos setting you choose. The distinction between "high quality" and "original" should only be made for photos and videos that don't fall under Google's limitations.