Your link itself admits the 0.05 makes it a different formula. Both Y and L* go to zero for hard black which is a very common color (the most common for me) and would be infinite with black in there. I disagree this is all "not real".

The 2x2 table in that contrast experiments link I sent enumerates some differences along the edge cases { even with just |diff|s. }. Just empirically if you change that 0.05 to 0.02 or 0.10 things change "a lot" in terms of all the edge cases. You can try fiddling with running that Python script yourself and see.

Also, I believe the project of an actual "contrast measurement" - not merely threshold checking - is a worthy goal. I think it would be good to be able to say how bad, and for that the specific monotonic transformation absolutely matters, and again, I expect the color space designer people have opinions on this very worth listening to. I think they are targeting differences in the numbers being the most meaningful thing.

All that said, I did like your George Box quote. :-) I just don't think dismissing the problem is a great solution here. I'm not sure there is a great solution. But you & anyone are always free to find any problem uninteresting. I mean, you could also find all the color space distinctions of TFA similarly "no real difference".