Not that I always agree with Michal, but I don't think he's being racist here. You have painted almost the entire Eastern Orthodox Church as "Nikonian" and "Sergianist" and basically *not the Orthodox Church*. Unless I've missed something, the only real Orthodox according to you are the Old Believers, and that's an exclusively Russian phenomenon. Theirs is a particular form of Russian Church and culture, while all the others you have dismissed as non-Orthodox have many cultures and traditions.
It's not a jump to presume that joining such a group would entail to a great extent "becoming Russian", and it is not strange to marvel that non-Russians would be attracted to the faith and lifestyle, question why, etc.