I wasn’t suggesting that. When you get stuck out in the middle of nowhere you can only buy AA batteries. So your equipment better use it.The Ultra casing would actually be able to fit up to four AAA batteries, in theory. One AAA battery should have roughly the same battery capacity as the Ultra battery, in terms of Wh.
A friend of mine found that recently when she couldn’t find anywhere in Tibet to charge her power bank up to charge her watch and phone from. But you could buy some hooky AA batteries for her eTrex!