The headphones in question are only for doing work while travelling. What I mean is they will be used while travelling on trains (Switzerland here you know), hence the decision for closed back to help isolate. It probably won’t be so much actual mixing (which he primarily does here in my studio in a properly configured monitoring environment) but rather for evaluation and decision making etc while en route.
There are many headphones which would fit the bill in this case, primary consideration being they should not be too bassy which so many headphones are.