If you shoot raw, the WB is meaningless. The K values express a range, not an exact color. Every raw processor uses different math and processing to produce the same results. In a nutshell, I don’t see how this would be useful for raw shooters. Film had a very fixed rendering thus using such a meter, and assuming the recipe for compensation filters worked, that was then a useful instrument. Not so much today.
Now if you could get true spectral color info, and then somehow build an on the fly profile (DNG profile ideally for many), such an instrument could be quite useful.
I think it's smart and very useful to dial in the Kelvin on the DSLR.
This way, at least the JPGs out of the camera are closer to neutral/desired balance.
The RAWs are also closer in case the client or retoucher doesn't use your same workflow
where the neutral balance setting resides in sidecar file as in C1 or Lightroom.
Also, when tethered there's an instant where the color could be [way] off/wrong
before the capture software applies the correction.
Why not avoid that dance altogether, and the inevitable question from the client or creative?