Ex. This article from 2013 where they talk about searching for [my photos of flowers] https://search.googleblog.com/2013/05/finding-your-photos-mo...
I'm an iOS guy, and don't have an Android device to confirm it. I've got a few photos visible on photos.google.com and they're able to detect "beard", at least. Which, to be fair, it's just a few selfies.
iOS does this pretty well. I searched my phone and it was able to recognize and classify a gun as a revolver from a meme I'd saved years ago. That's not this CSAM technology, just something they've been doing for years with ML.
And the only reason I know about them is because my wife asked about them and why our iPhones dont do them.
But we don't put stuff on Facebook. Our photos are backed up to our NAS. Phones backup to a macmini only. Siri and search are basically disabled as much as possible (we have to somewhat enable it for carplay) but definitely no voice or anything.