Depends on what your preconceived notion of 3rd eye and openness is. When I did meditations to open my third eye, instead of feeling what the lessons described of ''opening'' I felt that it was already open. So, it was never closed but I just never knew it. Maybe the meditation was only a way to focus that experience, so the 3rd eye is more of a construct than a state of being.
Robert Monroe had several out-of-body experiences by accident. He never bothered with third eye meditation before then. Maybe it was ''open'' without meditations, but if he didn't believe in it at all, then perhaps it doesn't matter.
I think all you really need for out-of-body experiences is a calm mind, a disjointed proprioception, and a way to trick yourself into giving up. If you vibrate and separate without third eye stuff, then the proof is there.