Just went through the whole Gridanian story and I think you're right. You first see Fye in an Echo instigated by adult Khrimm, though the game uses the same character models for the the two children who ask you to escort them in the present and Fye/Khrimm in the past, so I can see where that would trip some people up.

Fye then seems to recognize you enough to open up to you in an Echo instigated by the carpenter lalafell. One could write this one off, but then the instant you delve into a different echo, this time instigated by the padjal at the CNJ guild, she recognizes you as friendly and calls you by name.

Clearly your presence in the echo has cumulative effects and is thus probably the true past, not someone's individual memory of it, not a copy of it, but the real, actual moment in the book of history.

Interesting side-notes: No horns aside from that which the Moogle carries, which seems inconsequential. No obvious ascian activity aside from (possibly) the shadow which takes out several Wailers. Yet again, the archons realize your power due to the event of an echo within an echo.