The endnotes are essential, deliberately disruptive architecture
(on the direct reading; the fallback framing was not needed). Riders, adopted: the four-functions synthesis is held as four compatible readings, not four attested intents; and a composition note — the endnote apparatus dates to April 1994 (see the manuscript record's endnote-system entry), which caps any "conceived as architecture from the start" gloss (a guard; no such claim is currently on record).
Where readers stand
consensus
consensus (the only fight on record is about the audiobook medium, not the claim).
In plain terms: the endnotes are essential, deliberately disruptive architecture -- not a gimmick.
Where the text lands: strongly supported. Among readers: near-universal; the only fight on record is about whether the audiobook should have omitted them, not about the claim.
Three distinct in-text mechanisms carry it: the endnote-to-endnote cliffhanger relay between notes 324 and 332, note 324's nested sub-apparatus, and the Hal-transcription machinery -- with the author's April-1994 pitch as heavy corroboration. On the 1996 tour tapes Wallace stated the design himself -- it is a very different book depending on whether and when you read the notes -- and when a later round of proposed cuts fell mostly on the footnotes, he chose to keep about half. A composition note: the apparatus was invented in 1994 as a length-management device, which caps any "architecture from the very start" gloss. See Structure and Hamlet.
The question
This reading answers the crux what the endnote apparatus is for.
The ruling
Weighed in the adversarial ledger The Novel's Structure.