As per your own quote "The theory was players would retire and never play those low-salary years, meaning the player would have received more salary than the team was actually charged against the salary cap."
That means it can only be a cap circumvention contract if the player doesn't actually play those years out. If the player finishes his contract in it's entirety - aka plays every single year, then there's no possible way that it's a "cap circumventing contract", as the player was paid 104,400,000 million dollars to play for 12 seasons (Crosby's deal). If he plays out all 12 seasons... there's zero circumvention happening.
The only way it could be circumvention is if Crosby after the 2021/22 season when he's 34 years old (going on 35) decides that getting paid 3m over the next 3 years isn't worth the effort and decides to retire from pro hockey. Then and only then is it a cap circumventing contract. But until then, it's just a long term contract that pays out less in the end then it did at the beginning. And as you can see from my other POST there's clear advantages to both the team and the player to structure a contract like that, that have nothing to do with attempting to circumvent the salary cap.
