My father was blind and piano-tuner (besides his job as organ-player). Blind people are often educated in institutes to become piano-tuner. He certainly was highly sensitive. No the easiest person to live with, to use a euphemism. But in playing Bach and in piano-tuning he was really good. People loved his tuning. He had a vast list of fix "clients". Among them a producer of rock concerts, so he also tuned Stevie Wonder's or rockband Queen's piano, he tuned the piano for the Queen Elisabeth Contest when the "normal" tuner was not available... I know he had very good "ear", ear for "well-tempered" tuning, ear for timbre, colour, power, clarity, he was really a music-passionate. (one of his favourite hobbies was to get to the organ of churches, cathedrals)... He was a perfectionist. Frankly, since I lost my father and our piano (I have already a new piano), believe me ;I never had my piano tuned as good as the one we had at home when it was tuned by my father.
Are there bad blind tuners ? Most probably. Just as there are bad "seeing" ones. My last two tuners could both see, but frankly, they are not as good as my father was.
Very kind greeting to you all.