I've always honed my own razors and I find the HHT to be useful. I enjoy these types of threads because the HHT appears to be one of those things that is so cautioned against by experienced honers. I have a few thoughts:

Of course the shave test is the only thing that technically matters; you want a razor to be able to comfortably shave your face.
I submit, though, that by the time you've put razor to face, you've left the realm of "tests" and entered the realm of shaving. Let me make a crude analogy. To see if your supposedly-repaired printer is working properly you don't click "print" on a 275 page article, you first print out a test page. The HHT is the test page, and the process of prepping, stropping, and shaving is the printing of the article that you ultimately need.

You want a good indication, before you've gone to all the trouble of shave prep, that your edge is ready to go. A well-calibrated HHT will tell you that.

Even if I would consider my first shave with a newly-honed razor to be a "test" I'd have to shave my entire face with it. Doing a vertical WTG sideburn pass is not very informative, certainly not moreso than an HHT. What separates the men-razors from the boy-razors is the ATG chin and moustache areas. By the time I've shaved my moustache, I've shaved my entire face, and thus it's not much of a time-saving test.

I can understand why Guy 1, who hones a razor for Guy 2, doesn't particularly want Guy 2 to rely too much on an HHT. Maybe it's a bit like looking a gift horse in the mouth. I could see that being especially aggravating for Guy 1 if Guy 2 doesn't know much about horses in the first place!