Is it possible that alkalines and carbon-zincs will leak in different contexts?
In my experience, you better not forget alkaline batteries in a device for extended periods, they'll almost invariably leak.
Carbon-zincs do leak, but very often did I open up the battery compartment of some device, found 20+ years old carbon-zinc batteries in there, and they were 200% dead, but cosmetically pristine. One recent counter-example was some sort of battery-powered fan for camping. I suspect the batteries were quickly drained, giving enough time for the magic juice to be released instead of the batteries just drying like raisins.
Just a hypothesis though, I'm no expert in the battery department LOL.