I think part of the change (at least from a year or so ago) is that on the main analytics page, the traffic sources used to display percentage by view time and now it's displaying percentages by watch time.
By watch time my percentages for the last 28 days are:
31%- search, 26%- suggested videos, 13%- external videos, 31%- other
But in the same time frame for views the percentages are:
26%- search, 28%- suggested videos, 14%- external videos, 33%- other
So if I looked at it a year ago, how it's displayed would be different even if the percentages weren't changing.