The pilot did not seem like he was even remotely expecting the second helicopter from the left.
It is possible that the pilot of the landing helicopter heard what radio calls were made by the departing helicopter.
It is also possible that he was expecting the departing helicopter to have departed from one of the landing pads that the pilot of the landing helicopter was tracking to. This would place the helicopters on diverging tracks.
If that is what he was expecting, he would be looking to the right side or the South side of his machine for the departing helicopter which would track South. From the video, this appears to be the case.
The fact is that the departing helicopter departed from a helipad to the North of the intending landing pads for the landing helicopter put both helicopters on crossing tracks.