Just my opinion so not necessarily authoritative but it makes logical sense to me that in order for a religion to be considered Christian, those associated with it would have to subscribe to and accept the tenants in “The Apostles’ Creed” which is the Christian statement of faith for all, not just Catholic Christians.
"I believe in God the Father Almighty, Maker of heaven and earth.
And in Jesus Christ his only Son our Lord; who was conceived by the Holy Spirit, born of the Virgin Mary, suffered under Pontius Pilate, was crucified, dead, and buried; he descended into hell; the third day he rose again from the dead; he ascended into heaven, and sitteth on the right hand of God the Father Almighty; from thence he shall come to judge the quick and the dead.
I believe in the Holy Spirit; the holy catholic Church; the communion of saints; the forgiveness of sins; the resurrection of the body; and the life everlasting. AMEN."