Dave,
I think that these Alkalines only leak after years, and maybe preferably if they are not discharged, or used in low current applications, like remote controls.
That's what I experienced maybe 10 years ago, when I first found these batteries from ikea (Chinese origin), up to now. These Alkalines have about double the mAh capacity than other battery systems, and have a storage time of 5 years, the latest from VARTA AAA which I bought recently, even 10 years. Maybe they are not intended for low rated discharge, despite their long storage time.
My idea is that the liquid chemistry inside will deteriorate after years of storage, and may have a slow side reaction which creates this KOH stuff, which would not be produced by normal fast discharge.
Also, I don't think, that there is such high pressure inside, so maybe a real valve might not be used.
If you discharge these batteries quite quickly (and far before their expiry date), maybe a different chemical reaction sets in, which does not produce these crusty KOH crystals.
That's just speculation at the moment, so it might be helpful to understand the alkaline reaction path, either regular, or idle.
Then I have observed, that this alkalin stuff does not necessarily corrode metals, up to now it was a mess to wet clean the battery cabinet, but the spring contacts never were harmed.. copper surfaces maybe another story.
Here again, it would be interesting, which chemical substances emerge from leaking batteries, so to evaluate, which metals (or plastic parts) could be harmed.
Frank
PS: Yes, these chemical processes are sketched on the German WIKIPEDIA already.
In short, there's a side reaction (called outgassing reaction) which creates Zn(OH)42- and H2, which might be the white leaking stuff, and the gas which creates a bit of pressure.
This is usually a very slow process, but may be prominent, and much faster, if the Zn has a lot of metal impurities, like Fe, if the battery is not used, or under low load conditions.
That's also called a Zn corrosion process (due to the electro-chemical electromotive chain, why this effect happens)
Zn + 2H2O + 2OH- => [Zn(OH)4]2- + H2}
If you discharge the battery relatively fast, there will simply be no chemical stuff left for this side reaction and the leakage effect, as the KOH electrolyte and the Zn and Mn ingredients are consumed and turned into other, dry and non leaking substances.
In former times, this Zn corrosion was suppressed by addition of Hg, but as this is forbidden due to RoHS, it all depends on the availability of very pure Zn metal.
I suppose that even serious manufacturers like VARTA have still problems to get this, as they probably also produce in China, for example.
So I fear, Daves experiment on discharged batteries will not reveal any leakage effect at all, and the others might need many years before they leak.