He's got nno chance to be anything more than an injury fill in
With his signing, which C in the pipeline, can we no longer sign? Who has this signing impacted?
Do you think that the Marlies don't need any Centers?
Do you not think, it's important to have depth players, in case every other C in the organization gets injured, and at least there is someone to call up?
Do you think our developing wingers, shouldn't have at least good quality AHL C's and other players, to play with, to help their development?
In case you missed it, Leafs can sign up to 50 players. Many of those players are signed, with no intent of them player for the Leafs, except in extreme conditions. Maybe he's a late bloomer surprise, maybe not, but in the meantime, he was probably the best natural C on the Marlies this year, and likely will be next year too... and they need to ice a decent team, to help prospects that might be higher percentage guys. Unless somehow you think SDA should immediately expected to be the top C on the Marlies this coming year, or that such a prospect should have that pressure thrust upon them.
What you seem to fail to understand, is that there is far more to this, than just the Leafs main roster. It's the Marlies, it's all of the players development, it's about surrounding prospects with quality teammates, it is having cheap replacements in case of extreme injuries, and it's about giving a kid like this, who has thrived eventually everywhere else they've played a chance.