I also remember when people said Datsyuk and Zetterberg weren't "playoff warriors".I'm not sure I subscribe to that. I remember people saying Backstrom, Ovechkin and Carlson weren't playoff warriors because they couldn't get past the second round.
The same was said of Tampa before their back-t0-back cup wins.
Playoffs sometimes is a lot of luck. When you look at the history of cup winners, the vast majority of them have teams loaded up with players like Matthews, Marner, Tavares, Nylander, Muzzin, Reilly. When you look at the evolution of those cup winning rosters, you notice a lot changes in support cast from year-to-year.
It takes a while to find the right mix of stars and support casts. Some teams find it right away, some it takes longer, some never find it (the Sharks).
Any GM in the league would manage the leafs more or less the same, the biggest difference being that they probably would have passed on signing Tavares... though I'm not so sure.
It's just one of those things that take on a life of their own and then people start repeating it as though it means something.