I read the article; I don't think they highlighted this specific point that on-device scanning has a potential, hypothetical constitutional advantage in comparison to Google, Microsoft and Facebook who scan exclusively in the cloud.

They don’t draw out the comparison, but they do mention the protection.

You are right. But I think the distinction is an important one to make. People might not be aware about this critical distinction.

I did find someone in the media making this point, so it turns out I'm not being completely original: https://9to5mac.com/2021/08/10/misusing-csam-scanning-in-us-...