Another reason once again....that a back up gun alway's makes good sense.
Whoever designed the dump pouch (I have no clue) wasn't concerned with function, only form. The principle demand was to store and provide spare ammunition for the officer, period. The second demand was that it should be uniform in appearance. After that, practical deployment (real life reloading under fire) wasn't even a practical design consideration. I point to historical ammunition carriers, i.e. cartridge loops, typically used in the early 19th. century expansion of the American west on gunbelts, etc.. The design presumption was an ability to carry spare ammo to reload FROM COVER, for rifle, shotgun or handgun, which translated to the luxury of time and protection from enemy fire, while reloading. This was merely an extension of the sporting concept for conveniently carrying additional ammunition, such as in the instance of a hunter seeking game, and changed very little with no consideration of tactical applications in a gunfight for law enforcement. An exception may have been those early 19th. century hunters of dangerous game and their professional guides, who knew the value of having a "reload" in hand.
The dump pouch was merely a very minor improvement over the spare cartridge loop. From a design and engineering perspective it was little better than cartridge loops, but not by much. In fact, I believe the cartridge loop was superior, though more exposed to weather, especially given brass cartridges during the day, which suffered from verdigris in long term exposure to all kinds of weather. You old time street coppers know what I'm sayin'. Cartridge loops offered less potential fumbling. A box of extra ammo in the front seat of the radio car was just as helpful, providing you were in the car when you needed them.
Aside from having to qualify with a range reload, a second weapon or back up piece has always been a better solution to the fundamental challenge of reloading under fire. A well trained trooper (especially with a modern day auto loader) can get "re-heeled" in a milisecond. But with a revolver, especially, a second gun is the only way I would run.
Dump pouches were practical as spare ammo carrier's and that's all. If you had to carry them by regulation or department policy (I did) they were pretty useless. When I became a Sergeant, I remember inspecting service revolvers periodically and other equipment at the turnout or pre shift briefing before we turned out. There were guys who had so much verdigris on their chambered ammo, it was disgraceful, they couldn't even unload their ammo. The dump pouches, were even worse, green and stuck to the leather. Complacency, can make you dead, some got it.
Better to have than none at all I suppose, but speed loaders or spare magazines have always ruled the day in this century for a quick jump back into the fight. For me at least, it was always the 3rd. option....not the first....not the second.
By today's standard, the dump pouch is relegated to antiquity, from it's humble origin dating from the simple "possibles bag" drawstring pouch that contained spare lead projectiles from the days of flintlock rifles and muzzle loaders. Here's some good advice. Carry spare ammo, spare magazines, a speed strip or speedloader or two, but always carry a back up gun when travelling in harms way. I designed the New York Reload. What did you think I was going to say....hell yeah. Nuff' said.
Cheers;
Lefty