Without at all demonising how good of a ball runner he is, a lot of his big runs are helped by the fact that he takes the risky line between defence and the touch line. This allows him to get around or palm the winger but then often ends up either dangerously close to touch or having to force a panic pass back in field.
A great run isn’t as great if the overall outcome is poor. Cobbo will palm 4 guys and break 3 tackles while running sideward, get outside the winger and make a 10m break up the sideline before being bundled into touch and everyone, me included, will applaud how damaging of a runner he is.
It’s like if a player kept taking 60m field goals and impressed everyone with the distance accept he missed heaps of them. It’s impressive but not actually beneficial.