Breadth, not just density
A candidate who has spent a year on academic-style Japanese can still lose marks on information retrieval, because scanning a schedule for one condition is a different act from following an argument. The reverse is also true. N1 rewards a reader who is comfortable across registers, which is a slower thing to build than vocabulary and cannot be crammed.
The scoring structure is unchanged from the lower levels: reading is its own scored section worth one third of the total, with a sectional minimum you must clear on top of the overall pass mark, and it shares an untimed-within-itself booklet with Language Knowledge (Grammar). At N1 that booklet is the longest of the ladder.