He may be "experienced" but he is not educated in the sport.
I was taught to sit quietly after the shot(s) so as to not spook the animal. If it runs, let it go. If not spooked, it will quickly stop then bleed out.
I have heard of moose getting hit in the antlers and getting knocked down, then getting up in a minute. If the hunter is picking his way through the bush at that point, he could miss seeing it happen.
I recall shooting a moose at about 125 yards. It went straight down. My hunting buddy whooped and started running forward. I was doing my "wait and see". The moose got up, looked around, and sauntered off. I could not shoot because buddy was in line with it.
Turned out my moose was dead, but another had been bedded down by him. We could have had 2...