Also, if you've gone from zero to one of the biggest coroporations in the country, and have billions to throw at the 'metaverse', I find it hard to believe that removing CSAM is where you struggle.
Moderators need to actually understand the context of the picture/video, which requires knowledge of culture and language of the people sharing the pictures. It's really difficult to do that without hiring moderators from every culture in the world.
But small federated servers can often align along real world human social networks, so it's easier for the server admin to understand what should be removed.
My impression is it would take Manhattan-Project levels of effort and funds to come close to "solving" this problem, especially without someone getting on a watchlist for having a telehealth-first primary care provider insurace plan and asking for advice on their toddler's chickenpox.
Human review? Meta has small armies worth of content moderators already that tend to burn out with psychological problems and have a suicide rate where you're probably better off going to fight in a real war. (This includes workers hired by Sama in Kenya, to link back to the OP.)
I will reluctantly grant Meta that they're up against a really hard problem here.
It is a problem of their own making.