No they don't, they scan them on the servers. If you have a source that says otherwise I'd love to see. I'm 99.99% sure you won't find any.

If they are "uploaded to them", they are on their servers. They just do it there instead of before they are uploaded.

Exactly, and 100% Google and Microsoft have on device scanning as well. We are saying "Apple are bad for admitting it" what about the others that are not?

You have 0 proof of that other than conjecture. They are not scanning stuff and uploading it to government organizations to come and arrest you.

The point is that until devices and all their software/firmware become fully auditable, there's no way to be 100% safe, and we must resort to trust.

That wouldn't be a problem in an ideal world, but the one in which we live is far from even resembling one. Mining data is already a huge business, and governments everywhere would love tools to use to get advantage over people they don't like. There's huge motivation and demand for those tools at all levels, and at least governments have the resources to buy them and the power to force whoever implements them to stay silent. I'm not implying that spyware tools exist in any phone, PC, smart TV, car, etc. because we can't prove they don't; that's the argument used for UFOs, witches and unicorns, no thanks, but we better think like they do because technology, resources and demand for their adoption are real, and the rest is probability.

A literal feature of Google Photos is to find photos on your device.

Apple are not uploading anything to government organisations, in fact they are uploading less than google, by their own(and googles admission).

You have 0 proof that they are uploading to gov orgs… right?