Huh, I didn't get that memo so have been played a fool assuming 5v until now. Advertising mAh corresponding to a different unadvertised voltage than the output is just misleading advertising.

Then the fact we’ve “standardized” on mah as the unit is just another in our long proud tradition, same reason we still use “Watts” as the main measure of light output, even when it has to be made up for use on LED bulbs.

Could as least use Coulomb (or just count electrons), instead of taking Current = Charge / Time and multiplying by charge again.

For what it's worth: 1 mAh ~ 2.25 * 10^19 electrons. Or with SI-prefixes: 22.5 exa-electrons (= 2.25 Ee).

Mostly all flashlights advertise in lumen though? I suppose you mean light bulbs?

Yes, I mean the bulbs. Generally in the US at least we find them in the store labeled like "40 watt equivalent (small print: 2.1W)"