The divided line. I don't know. I don't much care for this adaptation of a conceptual-based language. I think it is the flip side of the Bible's general indifference to proof and argumentation. No one can prove anything about what the seer of Patmos saw, any more than any poet's.
Revelations is an insane rhapsody of a dream world of beasts and saviours.
It becomes true to the extent that we internalize it and act upon it. Those who have ears to hear will hear. The Bible, as we saw, is not good at these. The more metaphorical the account, the less you can prove or disprove. Revelations is best read as a dense mass of allusions to other visions, in particular to Daniel's.