Well its bordeline at slow idle - with brake lights lit. And we don't know how low the battery is. That's the point and why I don't want to condem equipment when not knowing the full picture.

As far as your not experiencing that, I beleive you.
Perhaps its because your car still has the correct equipment on it (not randomly rebuilt replacments) Or perhaps it because I drove a lot of /6 a-bodies. Only the /6 cars (maybe only the slant 6 a-bodies) got the lowest rated alternators as standard equipment. But I used to see this a lot when stopped at a light at night, especially with the wipers or heater on. I don't recall that in our '69 B with 318 and a/c - but it's been a long time and didn't drive it that much in bad weather. We replaced the starter on it, but as far as I can recall, alternator lasted its entire life.