I think GM's are quasi-colluding. If they weren't there would be more offer sheets thrown out there. If a player makes it to RFA status, there's nothing to lose by offer sheeting, assuming the player you would get is worth more than the draft picks you lose. If the player signs, you win. If the player doesn't sign, you drive up your opponents cap hits. Yet, we don't see offer sheets.
You don't see offer sheet......cause you don't have to.
Let's say we offer sheet Marner with a 12M - 7 years deal.
Marner goes back to Dubas with the offer and start negotiating base on that offer.
Then eventually reach a deal base on that offer sheet.
You won't still know about it but there was an offer sheet being made.
Sometimes fans forget that a player has to accept the offer to make it public and once it's public, even if the team match it or not, a media shitstorm follows that offer and every players are aware of it.
If i was a player, the last thing i would do is publicly accept an offer sheet.