I've noticed recently that a lot of AA and AAA nominal 1.5V lithium non-rechargeable cells are showing up on Amazon.

So far as I know, Energizer still holds patents on 1.5 V nominal lithium iron disulfide primary cell technology, but I think I've finally figured it out.

These new companies are actually using 3.7 V lithium-ion 10440 cells, and putting voltage regulators in them. These are not the same thing as the Energizer Ultimate Lithium L91 and L92 batteries, which do not have regulators.