I find it pretty ridiculous to assume that any dev would comment on the inner workings of their employers software in any way beyond what is publicly available anyway. I certainly wouldn't.
Why not? If I think my employer is doing something unethical, I certainly would. That would be the moral thing to do.
This tells me most of the people implementing this are either too-scared of the consequences, or they think what they're implementing is ethical and/or the right thing to do. Again, both are scary thoughts we should be highly concerned about in a healthy society that talks about these things.
One other potential explanation: FB and these large behemoths have compartmentalized the implementations of these features so much that no one can speak authoritatively about it's encryption.
You are talking about a company whose primary business idea it is to lock up as much of the world's information as possible behind their login.
The secondary business idea it to tie their users logins to their real world identities, to the point of repeatedly locking out users who they live under threat and refuse to disclose their real name.
