Uhh... I think the point is that if a player with an opt out to a multi-year guaranteed contract underperforms, then he will not opt out, and the club is on the hook for the entirety of the multi-year contract.
Unless I'm missing something, I think Austinfan is right about the risks here. If the player is good, he opts out and gets a big contract from somebody. If he's bad, he doesn't opt out, and he gets paid for the life of his contract, even if he's at replacement level (or worse). The player takes no real risk here.
The club risks being stuck with a bad multi-year contract. If the player is good, the club gets one year of good performance. If the player is bad, the club gets multiple years of a bad contract.
This can work for the club if the player is good, and that one year is worth the first-year salary plus posting fee, plus any signing bonus. But the risk if the player is bad is all on the club.