Who doesn't like Sandin? Playing well last year as junior aged player in the AHL. And certainly he has played well in the exhibition schedule against AHLers and not yet season ready NHLers.
All logic would say he isn't NHL ready in October. Best thing for him was to play against the # 1 lines in the AHL and a heavy dose of PK...preparing him for the NHL. The fact is that believe or not, Holl and Marincin are probably better NHLers than Sandin right now.

I'm not sure they can keep him up all year, as he likely has playing bonuses that they could not afford to hit the cap

Dubas and Sandin's agent agreed on no playing bonuses to avoid this exact scenario. Gets him to the NHL sooner and he likely makes up for it in his first contract

And P Bonuses payments can be delayed till next season's cap.

Yea I was thinking of next year's cap with only Reilly under contract and the cap not expected to go up much. I didn't realize his contract didn't have any bonuses on it. Then keep him up for as long as he is playing good.