He's not advocating that we un-invent the math that underpins crypto, so there is no way to prevent all crypto. I interpret his words to talk specifically abou

He's not advocating that we un-invent the math that underpins crypto, so there is no way to prevent all crypto. I interpret his words to talk specifically about people who choose not to add their own crypto layer on top of the OS / provider product layer. "opt-in" could mean the provider makes it available to the user, or (IMHO more likely) it could mean the average Joe that is unfamiliar with setting up a secure communication channel on their smart phone would not likely go through the hoops of learning to do just that.