He certainly, deliberately, grabbed him around the leg to make sure he fell. That isn't against the rules though and would have been because of the size difference. I think he would have struggled to hold him.Why couldn't he just wrap his arms in a bear hug type tackle and hold it in?
Do you really think the next player in Cockatoos situation should have free reign to do the same thing and concuss a player?
Just as the high bump you get a split second to do something reckless or look out for the other players welfare.
Worth looking at and agree it contributed to the injury. I just don't see it being illegal as things stand though.
Interestingly, while looking for footage via google, the search brings up videos of Cockatoo being reported for a sling tackle in last years round 3 of the NAB series. He has pre-season form, it seems.