1 Corinthians 1:12-13 What I mean is that each one of you says, I follow Paul, or I follow Apollos, or I follow Cephas, or I follow Christ. Is Christ divided? Was Paul crucified for you? Or were you baptized in the name of Paul?
Denominations are not the body of Christ. one's denominational affiliation is not important when one follows Christ. I can worship anywhere from Baptist to Pentecostal and I do.
My guess is that he’s Jehovah’s Witness/Christadelphians or something like that because he’s embarrassed to identify. They like the word ecclesia, too.
Is he Trinitarian?