Not always. I have monocular polyopia, which makes me see a minimum of 15 partial images of one object in one eye. Nobody knows what to do about it except glasses. And I see out of one eye or the other consciously, or use them together. Because of the differences in each eye, the stereoptic vision is split, or unsealed except under certain viewing situations.
Like anything else, assumptions aren't always true. Just like people think that I can tell you what instrument is being played at what note or what song is being played just by feeling it with my hand or body (rarely anything above a trumpet can be understood this way by touch, never mind felt across the room).
