The report you're referring to by the European Commission [1] shows that the mass surveillance of Chat Control 1.0 is probably not very proportional. They even note themselves that "The available data are insufficient to provide a definitive answer to this question".

However, the "13-20%" that you're quoting is a dishonest propaganda number itself. It's the false positive rate that a single small company (Yubo) reported. The reported false positive rates of other companies are between 0.32% and 1.5%, which is still a high error rate in absolute numbers.

Just to be clear: the report itself is full of uncertainty, convenient half truths and false causality. They for example completely rely on Big Tech platforms themselves to count false positives when a moderation decision was reversed. Microsoft apparently even claims that no user ever appealed against a decision ("No appeals reported"). There is no independent investigation into the effectiveness of the regulation at all, while it is in direct conflict with fundamental rights and required to be proportional to its goals.

The section about "children identified" is also a complete mess where most countries can't even report the most basic data, and it isn't clear if mass surveillance contributed anything to new cases at all. But somehow they still conclude "voluntary reporting in line with this Regulation appears to make a significant contribution to the protection of a large number of children", which seems extremely baseless.

[1] https://www.europarl.europa.eu/RegData/docs_autres_instituti...