Oh, they do. Maybe you should take a closer look at their construction.

Do you mean they try to make the lights small, or that they like button tops? Which ones like button tops? If you mean small lights, the program doesn't sound successful.

If you want a short light, try the FFL Z1 that is to be released soon.

https://www.firefly-outdoor.com/collections/ffl-flashlights/products/z1-artemis

That light is 92mm long, which is 65mm+27mm (27mm of stuff beyond the battery). Compare to the Fenix E16 that I linked above, which is 51mm=34mm+17mm. The Z1 is 10mm longer than an extended (and thickened) 18650 E16 would be. Plus add a 1mm or 2mm penalty to the Z1 for requiring a flat top which the E16 doesn't (its recommended cell is a protected button top 16340 with USB charging). They aren't making an effort.

Added: I'd say though that if you're willing to use an 18650 or 21700 light, you're really not after a small light (that's why 16340 and other small sizes exist). So trying to minimize an 18650 light's size by limiting battery interoperability is yet more foolishness. I had always thought the purpose of flat tops was to facilitate welding tabs for multi-cell packs, and none of these flashlights make use of that.

Hmm, another reason to require flat tops might be to prevent the use of protected cells, which afaik are all button tops. The protection tends to limit current, which gets in the way of lumenitis. Ugh.

Don’t assume, it’s easy to find photos of the batteries online. What do you see?

Wurkkos 21700 are available in both varieties: https://wurkkos.com/products/21700-rechargeable-battery-5000mah

But, that doesn't say what they actually ship in lights. Photos of that might exist but it's not super obvious where to look. I can say I've bought around 4 Wurkkos 18650 lights, one Fenix 18650 light, and one Wurkkos 18350 light, and ALL came with button tops.

Sure, if you want to crush your driver. The flashlight is made for flat top batteries.

Yeah I'd be a bit careful and gentle in testing. Though come to think of it, my D4v2 has already crushed the terminals of some FLAT TOP 18650's, so maybe I better not even try button tops.

I'm tbh getting tired of "enthusiast" lights, which appears to have become a synonym for lumenitis. I just want a sane non-enthusiast light with Anduril, if that isn't a contradiction in terms. Sane = among other things, no thermally unsustainable modes, no gratuitous battery incompatibility, and no excess mass added to the light just for heat sinking.