It does feel counterintuitive, no two ways about it - but as you said, it does work. I've been experimenting with doing the same "reverse highlight" thing on other colors for a "spectral flame" look in blues, greens, or purples, but I'm not happy enough with them yet to try a showcase.
Might be the picture/light, but the sencond huge elemental seems a bit too light though.
Bit of both, probably. The image was under too much light against a light background, and I'd gone a bit too pale in the base yellow in an attempt to get a superheated look. Sold it off ages ago so no chance of a better take on it, but maybe I'll take another stab at it in the future sometime.