Here's the thing, y'all.
If CAR doesn't make this offer, then JK is stuck with a $2.5m bridge deal, or a low QO, or arbitration, and he's stuck for 3 years. He's cost controlled by MTL.
JK has nothing to lose. He knows he's not worth 6.1, but that doesn't matter, because the 6.1 is just the mechanism to force MTL's hand.
Even if MTL says no, and they should, then CAR pays 6.1 for one year when they've got the cap space to do it, and then at the end of the 21-22 season, CAR says "ok, like we agreed, we're not making you a QO of 6.1, so let's figure out what you're really worth, and if you don't agree you can go UFA and no hard feelings." Thus getting exclusive negotiating rights for his *actual* value, and likely some goodwill for freeing him from the MTL org.
Worst case for JK, he's a UFA at 22, almost certainly making more than he would have been making with MTL.
This 1 year offer sheet was nasty genius. The fact that it was revenge is just the cherry on top.
Maybe y'all should have played that kid more than 13 minutes a game.