It's fairly common for our people to refer, in English, to the EO collectively as "the Greeks". It's simplistic and technically inaccurate for a few reasons, but it's a shorthand. It's like how native Greeks, upon hearing I'm OO and having it explained to them what that is, call me a Copt, or how native Russians have called me Armenian. Well, no...but I get it.
Back to the OP, in the only cases I know of where an OO switched to EO (or where an EO switched to OO for that matter), the reasons were more "pastoral" than "theological". So it wasn't a "change" the way it would be if a Baptist became Orthodox. For lack of a better word, it was more of a "transfer".
That said, I'm not sure where Extreme Copt's question is coming from or even what he's really after. There's always some faction of every Church which feels they are right, others are wrong, and everyone else should join them. But you don't decide these things based on who screams the loudest. Maybe s/he can explain a bit more what they're interested in? At least that way we can get past the tangent about "Greeks".