premise: The interdimensional hypothesis (IDH or IH), is an idea advanced by Ufologists such as Jacques Vallée that says unidentified flying objects (UFOs) and related events involve visitations from other "realities" or "dimensions" that coexist separately alongside our own. It is an alternative to the extraterrestrial hypothesis (ETH).
hypothesis: Jacques Vallée is a full fledged supporter of extraterrestrial hypothesis today.
reason: The statement does not say if Jacques Vallée believes in extraterrestrial hypothesis in the present day.