It’s because his language does not suggest a dispensational perspective. That plus his church choice, plus his background all add up to something other than dispensationalism to me.
There is also the issue that many consider this a purely apocryphal, unsubstantiated story that was put out by enemies.
My sense is that there’s “some” truth to it, but that it has all the earmarks of a story told and retold and grown distorted in that retelling.
Besides, it makes perfect sense if one is in a mainline denomination where there is zero emphasis on eschatology to find a book or preacher and adopt the latest fad. Especially one that sells lots of books.