I think the context makes it pretty clear its talking about lithium-ion rechargables, rather than lithium primaries.

I carry a D10 as my every-day torch, and wouldn't hesitate to get a D20 if I needed that form-factor. I normally run it on Eneloops, and it lasts over 50 hours on low, about an hour on high, on a single charge. Low is about 2 lumens and high about 130. (The D20 obviously differs.) It can also run on a lithium AA, or on any alkaline that I can scavenge from other equipment. It's battery versatility is a major benefit, especially as you only need one for the D10 - a spare lithium AA is light and takes up little room. The range of brightness is another benefit. I've left it on high for the full hour; it's a practical torch for outdoors walking the dog etc, as well as indoors long-term survival.