But that doesn't cause any cult-related concerns.
The part that makes people concerned about the potential for cult-style issues is the "British Israelitism."
That part is explicitly racialist to begin with, and since it is so strange, so ahistorical, and so closely related to other movements that are definitely cults - like Christian Identity - it is heart of those concerns.
Granted with a caveat. Since the trinity is a doctrine that evolved over several centuries after the death of Christ by what became the Catholic church. Protestants decided to keep this tradition. However the trinity doctrine isn't a "Christian" belief, rather it's a TRADITIONAL Christian belief. There's no doubt that bible Christians had no clue that a trinity doctrine was going to developed.
I would be glad to identify myself as a biblical Christian or a 1st century Christian to make that distinction clearer.