pic: 2016 Championship Alliance Selection Rates by Qualification Type

[Basel A]

Originally Posted by Chris is me

Another factor to consider is that this year, being an alliance captain required a slightly different skill set than being the consistently highest scoring team at the competition. Being able to guarantee breach and capture inflated the ranks of particular classes of robots, particularly highly mobile low goal scorers, so more of them were top seeds. This is in addition to the normal variance caused by strength of schedule, strategy, reliability, etc.

As seeding has gotten more accurate over the years (largely because of more matches?), 1st picks have gotten less good compared to their captains. This effect you mention is probably the only reason they were better this year.

https://www.chiefdelphi.com/media/papers/2843