[itsahoot]

But then where is any indication that John meant anything other than what he literally saw in Revelation

Actually John states that Revelation is from Jesus Himself, John only recorded what he was told.

[T Minus Four]

1 The revelation of Jesus Christ, which God gave him to show his servants what must soon take place. He made it known by sending his angel to his servant John,

2 who testifies to everything he saw—that is, the word of God and the testimony of Jesus Christ.

3 Blessed is the one who reads the words of this prophecy, and blessed are those who hear it and take to heart what is written in it, because the time is near.

Revelation 1:1-3