Well.... they're getting it from the NHL rulebook.
Maybe if you understood the actual rulebook instead of telling the people posting the actual rule that it means f all.
83.3
http://www.nhl.com/nhl/en/v3/ext/rules/2018-2019-NHL-rulebook.pdf
"All players of the offending team clear the zone at the same instant (skate contact with the blue line) permitting the attacking players to re-enter the attacking zone"
Skate contact with the blue line is enough to tag up in the NHL, according to their rule book. I don't know where your false rules are coming from though. Shoot me a link though, would love to see it.
Edit:
At this point it's whatever.
Don't agree with the call reversal personally. At least based on the evidence available / that has been shown, the league might have different or better quality shots that they haven't released. What I've seen hasn't been enough to overturn the on ice call (at least in my opinion).
There was time for Colorado to even the game afterwards, they didn't. It's an unfortunate ending to the season, but an enjoyable run. The call didn't decide the series (although it still stings)