P: Inconsistent results when copying white balance between raws & JPEGs via Sync, preset, & the SDK

The team has kicked this back as "as designed" with the following explanation:

"The difference in behavior is because, in some workflows, the full negative is available; in others, only the metadata negative or no negative is present. In this case, when WB is being applied across Raw and non-Raw images, the full negative is needed to get the correct result. So when preset is applied to a single image in Develop, it works fine because it will use the current full negative from the controller. But suppose the preset were to be applied in Library using QD or even from Develop but on multiple images. In that case, it will use metadata negative only, which will give different results. The same is true for Copy-Paste workflow. For SDK API, settings are pasted verbatim but since JPEG's WB values are not valid on Raw image, it doesn't change anything. Changing this behavior would incur a significant performance hit of loading full negatives for all the operations."

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"Translating temp and tint between raw and jpeg makes no sense. They are two different things."

By design, when LR copies Temp/Tint from a raw to a non-raw or vice versa, it picks Temp/Tint settings for the destination that approximate the visual appearance of the source photo.

Here's an example. The first row contains a raw and a JPEG exported from the raw. In the second row, the raw Temp was adjusted and its white balance synced to the JPEG.  In the third row, the raw Tint was adjusted and its white balance synced to the JPEG:

LR sets the JPEG's Temp and Tint to approximate the visual appearance from the raw:

Given that LR is designed to approximate the visual appearance when copying Temp and Tint between formats, the copying should (but doesn't) produce the same JPEG Temp/Tint settings (different than the raw settings) whether one is using Copy/Paste, Sync Settings, presets, or the plugin SDK. The current behavior was surely not intended by the product manager.

Note that copying the image-adaptive Basic sliders (Exposure, Contrast, Highlights, Shadows, White, Blacks) from raws to JPEGs and vice versa work analogously -- they approximate the visual appearance of the source image, even though internally they are using different computations for the two formats. Usually the differences between the raw and the JPEG are small but sometimes they are quite noticeable. (I warn users of my Export LUT plugin to use it with non-raws rather than raws for that reason.)

Thranslating temp and tint between raw and jpeg makes no sense. They are two different things.

I don't understand enough about the math of color science to know how hard it might be to get a good translation from Temp/Tint on a raw to Temp/Ting on a JPEG, or vice versa. But regardless of the quality of the translation, LR should give the same results regardless of how Temp/Tint is copied (Copy/Sync, presets, or the plugin SDK).

hm, so, is there actually a official "correct" translation between jpg<>raw? So far, I had the impression they are just pretty much independant and it is not so easily possible to translate between the values.