Yeah that is true about the cam cover but......................
If you return it to the block on the other side below the turbo, it will be ABOVE the oil line which is no good because the engine will naturally try to breath out it.

How he is doing it is perfect as he is breathing from both sides and oil is returning back to sump returning BELOW oil line .

I am doing actually this on my 4x4 and it is working fine

Luke