Justin Williams when he played with Luleå in the Swedish Elite League playoffs had one (1) assist in 4 (four) games. If he's got any magic powers they sure aren't working outside of North America. 23 (twenty three) games in three (3) Worlds Championships (in Sweden, Czech Rep., and Russia) and he's got 1 (one) goal and six (6) points. Hm.
Seriously though, both Justin Williams and Claude Lemieux have had the fortune of playing on some good teams, even giving them the opportunities to play in game 7s. That doesn't take clutchiness away from them but there's a reason secondary scoring threats such as Lemieux and Williams aren't providing game 7 magics on teams like the Florida Panthers, Phoenix Coyotes, et cetera, because in such a situation they would be 1st liners and you need to be an actual full package player (like say, Barkov) to build around and break through the heaviest traffic for something to happen. Claude Lemieux when the Colorado Avalanche won the Cup in 1996 had 12 points in 19 games, which put him at 9th place in scoring during the playoffs. On. His. Own. Team.
Justin Williams' had zero playoffs with PPG or better. Claude Lemieux had one playoffs with PPG or better.
Trevor Linden at least was a 1st liner on a good team and the 2nd best scorer on his team in the playoffs and went PPG or better 5 times. In his first eight year stint with Vancouver (when he was in his prime before injuries derailed his career) he had 80 points in 79 games.