I'd argue 13 minutes in the NHL has way more value to ultimate development than 22 minutes in the minors. Hardly a waste, and most young D men start on the third pairing as they learn, a natural progression. These kids aren't starting in the top 4.
That is a fair point. There are things that you can’t learn in the AHL, Babcocks system, game speed, etc.
However, at 20 years old I feel there is no need to throw him to the wolves in Toronto when the Leafs are desperate for defense and the team has Cup expectations. I would give him another year in the A, allow him to dominate, and give him top PP and PK duties to see how he works in different situations.
You are right though, if he plays on the Leafs in a limited capacity, it should not be considered a waste. That was poor wording on my part. I agree with whatever choice the team makes in regards to Liljegren, there are pros and cons with both choices, so make a decision and stand by it even if it goes sour.