Note: after reading the article through a couple times, I don't think that ammo load or type of weapon or even caliber are the primary arguments within the story. I believe the point of the story is more about situational awareness and close quarters tactics, 2v1. YMMV of course.
Going back to the OP, I think it's fairly obvious that 5 would not have been enough in that scenario. Of course, one could argue, "what if my revolver was a 4-inch .44 mag?" And I would concede that if the good guy in this case could place his first two rounds on each bad guy with a .44 mag, where he did with his Glock 21, then probably the fight would've been over right there. I believe this, because one of the officer's first rounds went through the bad guy's arm, into his chest and stopped near his spine. I posit that a .44 magnum round would've likely went through the spine, ending that guy right there. But the vast majority of people do not carry .44 mags and very few of those who do could place rounds as quickly and accurately as the shooter in question.
Anyway, it's likely that 5 rounds are not probably enough rounds when confronted by two attackers armed with semi-automatic rifles at close range. In fact, it's highly likely that the encounter would've ended far differently had the bad guys decided to stop the car 50 yards farther away and began their attack from there, making effective hits with a pistol much more difficult. Meanwhile hits for the riflemen would've still been pretty easy at those distances.
As far as the discussion of the thread so far, I only EDC a revolver with a speedloader when I'm hunting or fishing or otherwise "outdoors." Because most of the places I go "outdoors" there aren't people. In fact, most of the places I go the population of mountain lions is several times higher than the number of people I might run into. So a revolver carries enough rounds (no one ever is going to have time to reload with an attacking mountain lion whether its armed or not) to do the job.
Anywhere else I carry some form of semi-auto with one spare mag, with a load-out of at least 16 rounds, on up to 25 rounds. I settled on this number, after reading an article a few years ago that basically gave percentages for how often 3 rounds were fired in an incident up to 16 rounds fired in a single incident. Unfortunately, I can't remember the name of the article or even the exact numbers given for 3 round events, 4 round events, etc.
One of the things I took from that other article is that 10-12 rounds covered about 95% of all defensive shootings over a 10 year period. So it seemed fairly rational to carry at a bare minimum 10 rounds, hopefully in one mag so I wouldn't have to be coordinated enough to execute a tactical reload under fire. After all, I'm not Rambo or John Wick. Or Wild Bill for that matter. I'm a middle-aged freight pilot with a fetish for fly-fishing that likes handgun training.
However, I'm sure that several people reading this thread or dozens of members on this forum would argue that my 16 rounds in two magazines weren't enough "because . . ." and I wouldn't really be able to argue that. A person carries what they want for their own reasons.
I mean, I used to think that back when I lived in a tiny little CO town that I never needed more than 6 rounds out of a revolver (population was 1,100 or so); it's not like some nut would ever come into town and start shooting up the place with a M-16, right? Then Sutherland Springs happens. So who knows?