His contract was moved from the NHL bucket to the AHL bucket, but Comeau was never sent down. He never at any time was asked to drive/fly down to Cedar Park. He was told to go to his couch and enjoy collecting paychecks the rest of the season.
And? Players don't have to report to the AHL team. Lots of players refuse to report to the AHL team. That doesn't mean they are still "NHL property"
In this one particular scenario the Texas Stars aren't pressing for him to report/didn't suspend him for not doing so, and probably for good reason, they don't want that loser either.
But it's not like Nill just made it disappear.
And i'm sure if they really wanted to they could get him medically cleared, suspend him if he didn't report and cancel his contract if they outright wanted to.
But it seems like a situation where neither team actually wants him around, so everybody wins, but as far as anyone is concerned he's injured AHL property.
There is absolutely 0 cap circumvention.