Reilly can't sign with another team until July or August, right? Minnesota isn't having that great of a season, likely won't make the NCAA tournament unless they win the Big 10 tournament. So his season ends March 23rd. The Jackets can offer him the ability to play in the NHL March 24th. That would probably be a better deal if they were a playoff team. Handing whiny prospects NHL playing time on a silver platter without earning it isn't the best solution, but if Reilly is a must sign prospect...
The rookie salary cap limits the amount a team can sign him for, so he just wants the best opportunity so the next contract where he can cash in. And the more time he plays in the NHL, he more money he makes. But even Justin Schultz was sent down to the AHL his rookie year.
Reilly playing in the AHL Playoffs for Springfield this season to get a head start might seem more attractive than playing next season in the AHL, unless he believes some team will guarantee him that he won't be sent down. Considering he needs work in his own end, I wonder if a team would be willing to take that risk. Technically, Reilly could sign a ATO in Springfield to play this season, and end up not signing with Columbus.