The tech is an idiot. Yes the lifespan of you PSU might increase as it gets cooler air from outside however the system now not only have to cope with the heat it produces self but also the heat from the PSU and the hole computers lifespan will decrease.
Reverse it so it pull air back out again and if you are worried about system temp add fan(s) to pull in air from the front. There's plenty of room behind the front bezel to hide slim fan(s) and they can be placed near the cutout next to the zorro slots or you can drill a hole in the metal where you see fit (or both)... you can even drill holes in the backplates where there's no cards installed for better airflow over the cards that are installed.
