In a theological sense, doesn't that automatically exclude them from the Christian familiy?
If it's true, it certainly places them in disobedience to the Great Commission which Jesus gave to the Church just before his ascension. Jesus assigned a specific duty to the Church before he went back to Heaven to sit at his Father's right hand.
Mk 16: 15-16, "And He said to them, "Go into all the world and preach the gospel to every creature. He who believes and is baptized will be saved; but he who does not believe will be condemned."
There is no ambiguity in that charge to the Church, evangelizing the world is the duty of every Christian.
But I don't remember ever having read any passage of scripture that commands me to take part in worship of "Sophia", whoever or whatever "Sophia" may be. I tend to think that this entity called "Sophia" is no friend of our Lord or his Church. IMHO it's more likely that she, he, or it, as the case may be, has soot on her/his/it's face and smells like brimstone smoke.
Perhaps in an ultra technical sense, but I consider the UMC as part of the universal Christian church as long as the church professes faith on one of the creeds or all three.