Huh wonder which camera apps enable use of this API?

This is one:

https://halide.cam

This is VERY interesting and I am glad you posted this, as it is my first time coming across this.

To disambiguate, this is not meant as “added a mode to the stock Camera app”, but rather “added a mode to the camera API that iOS developers can use”.

That's so annoying it's not stock.

I always have to get a very bright flashlight to make rashes show in a photo and then the rest of the body looks discolored as well but at least I have something to share remotely :/

Thank you for sharing. Seems to validate my suspicions!

It's not really something to be suspicious of. Cameras just don't know what colors things "actually" are, mostly because they don't know what color the lighting is. Auto exposure/auto white balance erases color casts or unusual skin colors.

You can put a color calibration card in the picture to achieve a similar effect, but it's not as predictable.