Home screen orientation on 6 Plus used to allow holding phone upside-down, but this doesn't seem to work anymore.

One of the reasons I liked my 6 Plus was the Home screen orientation could rotate to either side or even upside-down. I didn't notice when it happened, but orientation still works to either side, but upside-down no longer works. Was this feature "fixed" in an update or is there a setting I may have accidentally changed?