It looks weird, thats for sure

And the APU exhaust is not from the no2 engine, since the APU outlet is located under the right stabilizer (correct Craig?)
Normal APU ops on the aircrafts I'm familiar with has the APU start up on the taxi-in checklists, so the APU is a non-factor here.
Maybe the no2 exhaust looks that way since the pattern is not obstructed. Both no1 and no3 has the flap system behind them which creates some airflow manipulation.
Check out this picture and you'll know what I talk about, pay attention to the outboard engine on the right wing