I feel they aren't to top off the weapon fast, but to put more rounds in as quick as possible in a small more concealable package to continue the fight when you run dry. Like you would 2 in one shot on a speedstrip, close and and go. Instead, it gives you three in one shot.
That's my take on it after years of training and practice.
I own four of them for my K frames
If you want fast complete reloading, use speedloaders.
I disagree for a couple reasons.
When "loading two, shooting two", an officer still had to index the cylinder to put those two rounds immediately to the right side of the frame, so they'd be next up when the trigger was pulled. That took, and still takes, some time and some fine motor skill.
With the K-Pak, it takes about as much time to just load the "bottom" three as it takes to index the cylinder so there's no real upside to not loading all six.
You can certainly do it that way, I just don't see any real advantage.
——
The "load two, shoot two" concept came out of the Newhall shooting in 1970, and other shootings similar to it where a bad guy counting rounds would know an officer's six shot revolver was empty, and where it took a long time to load six rounds individually without a speed loader.
In the Newhall shooting, one of the four Highway Patrolmen involved was shot and killed while single loading six rounds into his Colt Python. Head down, focused on reloading six rounds he didn't see one of the two perpetrators approaching him and was shot and killed while loading the sixth round just before closing the cylinder.
The working theory was that had he had a speed loader, he could have quickly reloaded without taking his eyes and or attention off the threat and been able to continue to engage the perpetrators. As as a result the CHP became the first major police agency to both allow and issue speed loaders.
The "load two, shoot two" approach was what ended up being recommended for departments that still *didn't* permit speed loaders. To be effective it really requires a speed strip, but it could be done with cartridges in belt loops or in a pocket, but not so much with a dump pouch, unless the officer dropped the other four in a pocket.
But, either way, it got the officer back in the fight, usually before an assailant counting rounds could rush the officer.
—-
There was still however a great deal of resistance to speed loaders and speed strips in many departments. 15 years later the department I worked for had a chief of police who was basically anti gun and didn't want to encourage officers to fire any more rounds than absolutely necessary.
It was the police version of the objection of some military commanders in the 1930s to adopting the semi auto Garand over the bolt action 1903 Springfield. They felt higher rates of fire encouraged poor marksmanship. It was similar to commanders a generation before who felt the 1903's magazine cut off should be engaged and the 1903 used as a single shot with the rounds in the magazine kept as a reserve, for the same concerns about marksmanship and wasting a mo.
Old ideas don't die off until the old guys who thought them up die off or retire.
Consequently our old school police chief didn't allow speed loaders or speed strips, but instead still issued just six rounds for use with a single dump pouch. (Six rounds, not even seven to allow a spare if the officer dropped one under stress.) The response from many officers was to just say "whatever" and carry a J-frame in an ankle holster. Those that did so figured they'd rather be fired if they ever had to use it, instead of being shot or killed because they didn't have it.
Most of the officers I knew in that department also carried a speed strip or two in their pockets and certainly had the option of a "load two, shoot two", reload. I'm not sure using non department issued ammo would have been any better employment wise however. But still better unemployed than dead.
Ironically the two perpetrators in the Newhall shooting prevailed partly because they had multiple backup weapons in their car. Without the option of speed loaders, we opted for an non approved backup because it works.
——
With all that as background, I'm of the opinion that for an armed citizen, carrying a speed strip with extra ammo in a pocket still works fine for insurance against the very unlikely chance that he or she would ever need a reload, given that almost all armed citizen self defense shoots are over and done in 5 rounds or less.
However, if I were carrying a K-Pak, I'd just load all six. The extra time compared to loading just three and indexing the cylinder is not significant at all.