And in fact I'm willing to bet that explains the divergence of opinion that the Senator noted in the linked story. He probably was told in his classified brief

And in fact I'm willing to bet that explains the divergence of opinion that the Senator noted in the linked story. He probably was told in his classified briefing that NSA could record and collect phone calls without a warrant. Mueller, on the other hand, would be talking about actually tapping into that data, which would need a warrant. I'm not sure I buy the argument that you can record a phone call without a warrant just because it's using VoIP or some equivalent instead of a physical wiretap, but it does sound similar to the other arguments that have been made to collect data for later analysis by warrant if necessary.