Woodcroft's Oilers and Knoblaugh's Oilers are massively different defensively, the Oilers play much more like the Crosby Penguins of a few years ago in the playoffs these days. Woodcroft was all about just run n' gun, Knoblaugh/Coffey instituted much better structure.
They're not the same team at all, if almost 70 games in the regular season wasn't enough of a sample size, four full playoff rounds and multiple game 7s more than proved it.
Even in game 7, Florida was held to only 2 goals, that's not too bad, generally if you hold a team to 2 or less you have a fairly good chance of winning.
Florida, Dallas, Vancouver, LA all saw their offense grind to a halt the longer all of their series went on against Edmonton. None of them could average even 2 goals per game flat in the final 3-4 games of their series'.
If that happens once, ok, but four times in a playoffs, no way does that happen just by random happenstance. You have to be playing within a structure to do that, the forwards in the league are way too good to be shut down by mirage defense, the coaching/scouting in the playoffs is way too good to not pick up on exploitable flaws.