Ennis has done at least three things that should've been penalties:
1. The high shot on McManus
2. Caught totally offside at marker, and you could hear Knights' players screaming it at the ref
3. After that no penalty for offside, he pushes our player just as he's trying to play the ball.
Some players and teams thrive off the knowledge the refs will only ever blow so many penalties in a game. They'll never let it get ridiculous. And if you can give your penalties away at 'good' times, like early in the tackle count or when defending your line under pressure, they all add up the same in the stats column.
If I was a coach these days I'd actually encourage my team to give away penalties at appropriate times because it can save you being penalised at more important moments later on.