Actually if you check you’ll see that I gave you both “adapted to D50” (relative, “-ir”) and “using D65” (absolute, “-ia”). I tried to indicate every step of the way which I was using, but I guess I didn’t try hard enough 
Hmm, see these two posts over from another thread:
Also see this article, in particular sections A3 and A4:
sRGB luminance: technology, standards, and color science which talks about “why D50”.
and this article, section D1:
Programmer's Guide to XYZ, RGB which has what I hope is an easy to understand “imagine this” that demonstrates what “adapting to the color of the light” actually means.
There is a common thread running through all of this, which is “What color of light are your eyes actually adapted to?”
In ICC profile color management, the assumption is not that your eyes are adapted to D50. The assumption is that your eyes are adapted to the color of white on your monitor in its current state of calibration.
ICC profile color management does indeed send “D50” values from the image to the monitor profile. The monitor profile in turn sends RGB values to the screen that are appropriate to your monitor’s actual state of calibration, if indeed you are using an appropriate monitor ICC profile that actually describes your monitor’s display characteristics in its current state of calibration.
@briend and @KelSolaar - Hopefully tomorrow I’ll have time to go through all of your calculations, which look really interesting. I’d very much like to add colour-science to my current list of “tools for exploring color spaces” and the provided examples are helping quite a lot.