If you take "white" light and filter out the wavelengths between blue and violet, 'selective yellow' is the result. If you don't know what it is, your company's lights probably aren't it. Also, since they are a yellow light, color temperature doesn't really apply.
Hey there, I'm Paul, one of the engineers here at Diode Dynamics. Nick asked me to help with your questions.
You initially asked whether the bulbs were selective or "ordinary" yellow, and frankly, I'm not sure what you meant either, as "ordinary" yellow, if it's really yellow, can only be physically produced by selective means with filament sources and is not too relevant when discussing LEDs. In my experience, "selective yellow" is the only
yellow. But in either case, in the automotive world, selective yellow is now defined by a specific quadrant of chromaticity coordinates, not by the method by which it is acquired. It's a good thing that's the case, because "selective" as a term no longer has much meaning when you're dealing with LEDs... they don't produce a full spectrum that has to be filtered out in the first place like is necessary with filaments.
Anyway, the yellow XML2 offers a nominal chromaticity coordinate rating of .48,.46, which would indeed be considered selective yellow by SAE and ECE standards (J583 and Regulation 19, with the added white allowance for fog lamps). As more detail, they have warm white LED emitters with a yellow filter (lens). The emitters used are Z8 binned CREE XML2, which is 2700K, which is then filtered by a lens, which produces a yellow color that has a nominal 3000K CCT. The dominant wavelength is 579nm. You're correct that 2700-3500K CCT LEDs naturally have a warm white color, but yellow is possible as well, and there are even some new chips on the market that produce a yellow light naturally with specialty phosphors.
Regarding your last statement, the use and brightness of fog lamps is heavily personal opinion and is related to the physiology of vision in general. If that's your opinion, you're certainly welcome to select a different option or discontinue the use of fog lamps altogether. If you haven't already, I would recommend reading this article written by a friend of mine, Daniel Stern. There is an argument to be had that fog lamps are never of value if the goal is solely increasing visibility. https://www.danielsternlighting.com/...fog_lamps.html