a long time ago.
But isn't the voltage under load the critical factor here? I dimly recall, perhaps correctly, that some battery assemblies (Li-ion) included a resistance arrangement to keep the voltage presented to the device in
while in operation to an appropriate level. That specifically had to accommodate the varying internal resistance.
I think Canon chooses not to recommend lithium batteries in P&S owing to variances among batteries and over time in internal resistance/voltage under load rather than open circuit voltage out of the pack. Alkalines, with the same nominal open voltage as lithium (~1.5V), were acceptable although Canon recommends NiMH. Can't go too far wrong as long as the nominal open voltage starts at 1.2V.