Everything you’ve said aside from the CSAM scan doctor thing has absolutely nothing to back it up so far. (And for the record, I absolutely agree CSAM scanners can be wrong—a human needs to be involved at some level, which they were in the system Apple devised. At any rate, I guess this convo is over as we obviously inhabit very different worlds.
I think iMessage and whatever Google had at the time were “good enough” here that WhatsApp never caught on? Like most people already had unlimited texting by the time it hit the scene, so It just felt like a scam back in the day and I remember it wanted my phone number to complete a sign-up and I was damned if I was going to give it to them.