Your religious beliefs typically depend on the community in which you were raised or live. The spiritual experiences of people in ancient Greece, medieval Japan or 21st-century Saudi Arabia do not lead to belief in Christianity.
But, as D.T. Suziki has pointed out, Meister Eckhart managed to arrive at something very like Zen without any direct knowledge of Buddhism, and the similarities among the various mystical schools can hardly be explained by social conditioning. Moreover, any reasonably reflective person takes into account such factors as one's upbringing, education, etc., all of which, as Gutting indicates, apply to other views as well.