” Most people cant make the distinction that we usually don’t need to rely on the CI”s chiddush in large cities today.”
Also what they are confused about is that they do not realize that the Chazon ish has two statements, and the first one as described above is simply, no argument, the psak of most poskim Achronim. The CI mainly mentions it to get to the next chiddush, but the first layout was פשוט to him as the final psak a reshus hayachid.
(Also, another point his statement indicates, that his simple understanding regarding 600k is, that they need to pass through ONE street.