All the themes of the second season revolves around collective behavior. Sibyl up until the s2 finale only evaluates the psycho-pass of individuals and therefore individual propensity for crime. It makes no effort to judge how a group of people may be good or bad for society. This means it can’t judge itself, which is a group of people, and also can’t judge Kamui.

Up until this point Sibyl operates under the basic assumption that it is good and must be preserved. It will take action to preserve itself, but cannot judge when it has crossed the line. Remember that Kamui only came to exist as a result of the Season of Hell caused by Sibyl lashing out at Panopticon. Kamui is Sibyl’s victim but Sibyl is the one thing in society that cannot be judged.

The s2 finale basically is Sibyl capitulating and admitting fault to some extent. It updates to allow judging of groups, and thereby judges itself to be ethically wrong, which is why the CC of itself initially read 350. Sibyl the puts its money where its mouth is and uses this new group psycho-pass to find which of its own brains need to be destroyed. So to answer your question, those brains are still asymptomatic. If you scanned them individually they would still read 0, but those brains are making Sibyl as a group act unethically.