Don't forget that for compensation purposes the total contract is divided by a max of 5 years. So 7x6 = 42 / 5 = 8.4 - compensation is 2x1st + 2nd + 3rd.
Pretty sure Chevy matches that and higher. An offer of 7x7,248,787 or higher triggers 4 1sts. I take the 4 1sts. $1 less than that and I match.
Edit: There is no guarantee that some team doesn't offer him less term - but if they want to ensure that Trouba signs it they probably need to offer both $$$ and term.
I suppose that if Trouba really wanted out he could find a taker at something like 3-5 years x 8.2 and hope Chevy doesn't match.
I don't see top end players being poached anymore with offer sheets. As you pointed out the compensation is just too high for a slightly above market value offer. Given the importance of ELC surrendering 4 firsts is not something any team really can do and hope to remain competitive in this environment.
Where I see the potential for offer sheets being successful is on the mid range player. A guy like Armia or Lowry would be targets. A 4 × 4 offer to Lowry likely takes him out of our price range but the team acquiring him is only paying a 2nd round pick if not matched.