But the time the Prophets experience cannot be a mere dot or a vertical line on such a diagram, or they would never learn anything, or would learn everything at once. And it needs to loop back on itself in funny ways to explain why Sisko is created only after he is encountered, in terms of the horizontal axis. Still, "funny" by no means equals "patently impossible": functions that loop back are merely more complex than functions that do not.
A far more simpler explanation is that the Prophets were pretending to not understand linear time (or corporeal time or whatever) just so Sisko could understand a little about them. This argument about the Prophet's creating Sisko after their first encounter is totally illogical. The Prophets must have seen a future with Sisko so they picked a present or something to create this future.
What is non-linear time? To be unconstrained by the fourth dimension and move through both space and time unconstrained, to see various pasts, events, presents and futures and to switch between them.