Stu says: "Six-on-five situations. NHL stats do an excellent job of breaking down the game and ice time when play is 5-0n-5, 5-on-4, 4-on-4, 4-on-3 and so forth. But there are no stats for when a goalie has been pulled for an extra attacker on a delayed penalty and a 6-on-5, 6-on-4 or the ultra-rare 6-on-3 results. Pulling the goalie is not officially a power play, but it is something apart from the normal run of the game and worth exploring numerically."
There are some mistakes that arise from not sequestering empty net 6-on-5 time from 5-on-5 time (primarily a lot of minuses for top offensive players playing with an empty net), but so little of the game is played with an empty net that I don't think we can draw any conclusions about team-level skill:
% of Empty Net Ice Time by Minute:
The average NHL team plays 15 seconds per game with its net empty. That's one period per season. Is one period enough to just an entire season for a team? The Columbus Blue Jackets would love it if their first period against Detroit on October 25 could stand in for their entire season.
Verdict: the NHL should collect this data, but only to maintain the integrity of non-empty net data.