It would never even occur to me to taste a meal while cooking it; I don't think my parents ever did when I was growing up so I never started, I wasn't actually aware non-chef people did.
I can't even see what I'd gain from it; maybe if I was an expert taster and cook I might be able to figure out if it needed more salt, herbs, whatever, but I'm not and I'd have no idea what to add/change even if I did taste a difference. Maybe a personal inability, it strikes me rather like singing - I know I'm out of tune but I don't know what direction to go to make it right; flavour is the same, I know when a meal didn't taste as good as normal, but can't tell what the difference was to change it.
Was EP a trained chef? I don't recall that being mentioned, but it's been a while since I read the early articles. I wouldn't automatically assume a non-chef to be in the habit of tasting, given just the examples in this thread (and those I've seen in my own family) of people who don't.