He is paid 7.5 per season. He just ends up working like 5.5 seasons instead of the full 6 in the contract.
It's insignificant for the cap, yes. It is not insignificant when Marner and Matthews and Kapanen look at his actual salary... which is 7.5
If you sign a contract that says you get paid $7.5 million per year, but you and everyone else knows you are only getting paid $6.9 million per year ...
How much are you getting paid?
Which number is more relevant?