All I know is it has to do with his groin, apparently he is behind schedule, and they probably don't want to rush him until he feels 100%.
Kaskisuo had a similar issue and tried playing through it. He missed a month, came back and sucked for a month a two, then improved a bit but was still inconsistent for another month or two, and then he finally was firing on all cylinders by March. He suffered the injury in mid-October. It was clear up until March that he wasn't 100%, and it likely took longer for him to get to 100% because he was playing through the injury.
I think the Marlies are looking at what happened to Kaskisuo and are not going to risk it this time around. He's a top prospect and wouldn't even be playing in the AHL. Besides, a bit of adversity will force the Growlers to focus on improving their defensive game, which will only help Scott when he does come back and plays with the Growlers this year.