Why? This is contradictory to the idea they have the clutch trait.
Nope, not contradictory. Let me reiterate the main part of my opinion.
They are players who have, throughout their career, shown that they perform well - maybe even to the upper level of their (limited) abilities - when they're in high pressure situations. That's a valuable trait in a player. Other players have shown the opposite - whether it's due to nerves, or deficient desire and motivation.
Some players - Talbot, John Madden, Kris Draper, to name a few - play at their highest level when the pressure is high. Playoff games. Elimination games. Third periods. These guys clearly feed off of the pressure in a constructive way, and enjoy the limelight. That's why they are great guys to have on your team in your bottom six. They check better, they make better plays in the defensive zone, sometimes they even chip in with an odd goal that you wouldn't have expected from them otherwise.
Other players do the opposite - they crumble under the pressure, they succumb to nerves, they grip their sticks too tightly, and make worse decisions , all because of the situation.
That being said, guys like Draper and Madden still aren't your top offensive players. They are your checkers who might help out with a little offense here or there. You want your top guys out there with one minute left to score a goal and tie the game. Hopefully - and it's necessary if you are going to be a successful team - your top offensive players
also raise their level of play when the pressure rises. Sakic, Messier, Yzerman, Crosby. Even the non-superstars who are in your top six - guys like Justin Williams, Claude Lemieux, Jamie Langenbrunner, Trevor Linden. Those are the guys you also want on your team, and those are the guys you throw out there with a minute left because they can score goals with frequency.
If your top offensive players are guys like Tkachuk, Yashin, Petr Nedved - all great scorers, but all guys who tended to struggle when the going got tough, or who looked uncomfortable when the pressure was on - then you're in trouble as a team, regardless of who's in your bottom six.
All of that in mind, that doesn't preclude the bottom six guys from being "clutch" (I hate that word) and raising their level of play in crucial games.