I would agree there are workflow issues, Bart, and would never contend that every method is equal. Quite the contrary, for instance that's why I don't care for Jeff's pixel layer approach (awkward if you then need some retouching or want to fine tune the raw conversion). I'd also agree on experimentation/alternatives and I like Lightroom/Silver Efex features such as the preview when rolling over presets and using before/after for benchmarking.
But I'm really not saying "it's the intended result that counts", which you rightly treat as banal. Instead I think the answer to the OP lies more in developing one's ability to apply the right criteria to help you drive whatever may be the best technique. For example, the OP points to the importance of tonal transition in the sand dunes. Well, you reproduce those in your B&W by knowing you have to pay particular attention to tones in the the brighter images areas because especially in B&W the eye is drawn from dark to light. Or take a less monochromatic scene than the sand dunes, trees in autumn colours - here the criterion that drives your B&W conversion might be to separate tones in the reds and greens so the B&W image conveys that the trees' leaves vary in colour. Another classic example is skin tone - do you want to emphasize facial features or smooth them out, and is that appropriate to how you want the subject to appear? It's also about thinking where the tones lie in the fame - do you want the light tones around the edges, the sky light or dark, the subject of your photo to be mainly in darker tones etc.
So while I agree we should dismiss processes that do get in the way, are hard to fine tune, or have other objective deficiencies, I'd put more emphasis on developing that kind of understanding of B&W.
John
