I used to be one of those that drip acclimated each fish. I've somewhat changed my mind.
My logic is that the water in one's tank is definitely healthier than the water in the fish bag or even the store water and after a long trip there's ammonia accumulating in the bag which becomes toxic upon opening that bag due to the CO2 escaping and raising the pH. Ammonia burns can damage fish permanently.
You can also suffocate fish if you acclimate them in the actual plastic bag due to the small surface area.
So sometimes it is better to just drain the fish in the net and pop them in. I've done it numerous times with no issues and I wouldn't be sure drip acclimating is always the best approach. If you're adapting soft water fish to hard water than yes, but when ammonia is involved one has to act fast.
I don't worry about temperature. A few degrees are no issue and if for some reason the temperature in the bag has gone down significantly it can't be a good thing prolonging the period the fish stays in that temperature. When I was a kid I happened to nearly boil fish with one of those heaters those days that had no thermostat that I had forgotten to switch off and popping the fish in the right temperature would obviously revive them. You don't temperature acclimate fish when they're in temperature they can't normally tolerate...The fastest you get them out, the better.
So I think your friend may have done the best thing in the situation...