Sorry that the documentation changes are lagging behind here, but here is an explanation of what is going on there:
The video_total_views metric within the VIDEO metrics group will report on any views which are at least 50% in-view for 2 seconds, as per the MRC standard. This will align its returned values to the existing video_mrc_views metric in the API. Data for this new metric definition can be retrieved for time ranges starting from 2015-12-01. This MRC view definition will be used for the default VIEW bid_unit for Video View campaigns.
Our original video view definition of 100% in view for at least 3 seconds will continue to be available as a new video_3s100pct_views metric in the VIDEO metrics group. To continue to bid and be charged based on the original view definition, use the newly available VIEW_3S_100PCT bid_unit.