You will never “rise to the occasion”, you will only devolve to your level of training.
I am by no means a first-hand authority figure on the matter, but one also does not need to be an astronaut to know the moon isn't made out of cheese.
But in studies, debriefings, and AAR's, the quoted statement has been proven true with little to no exceptions.
There's a reason every capable entity in the firearms world drills extensively on even basic firearm manipulation. Until the basic actions: Loading, reloading, malfunction clearing, muzzle control, and sight acquisition, are almost completely automatic. And because none of those require any thought, when the fecal matter is already in the fan blades, the only thing they have to focus on is lining up the sights and making their hits where and when they need to be made.
Adrenaline with narrow the vision (on average) to about 30 degrees referred to as tunnel vision. And with your thoughts racing, if you cant handle your weapon correctly without thought or taking your eye off the threat, you are way on the back foot. And since most self defense shootings put you on the back foot to start with, it wouldn't be wise to further disadvantage yourself.
Some may have differing opinions but evidential data by and large proves what cmshoot already stated. If your friend feels different, they are simply fooling themselves.