Yup all cloud providers have been doing this for a good 5 years or more now.
The big difference is the servers in the cloud are owned by someone else. Hence they can scan your stuff for whatever they want. Also there is a hard line, in that the cloud cannot actually scan anything you don't give to the cloud.
Scanning your personal property is a much more tricky situation. The best analogy would be if Apple announced they planned to come into your home and search your house/garage/property once a week....all without a court order, probable cause, etc. Oh and Apple won't tell you what they are searching for (they say it is for naughty photos, but they don't let you watch them search your house, or show you what is on their checklist of "bad items" - so they could really look for anything they wanted while they were rummaging around). Just because Apple makes the iPhone, that doesn't give them any more legal right to scan your device without a warrant than Ford can come and search your personal Ford car/truck.
I honestly believe that if Apple had gone ahead with this, it would have been an endless stream of lawsuits.