Apple already implemented a solution to scan content on your Device before it gets encrypted and sent to the cloud (Communication Safety feature) that is sitting in your phone since iOS 15.2. So, they don't need to have a look at your encrypted iCloud Backups, theoretically, they could always look at it on your device before it gets encrypted and shipped to the cloud.
They promise that none of those scans or resulting data leaves your device, but since it's a closed source platform, and you have no way to verify that claim independently, it all boils down to a single question.
Do you trust Apple?
If you can answer that question with yes, then making the most of the new security features is a no-brainer, as they significantly lower the risk of your data leaking in the cloud in case their servers get hacked or simply human error on their part.
If you can answer that question with no, don't own Apple devices.
