The 8 year/100k mile warranty is only for defects in workmanship. It does NOT cover premature degradation; that warranty is only 5 years/60k miles.
From Nissan's site...
"the Nissan LEAF® Lithium-ion battery is also warranted against capacity loss below nine bars of capacity as shown on the vehicle’s battery capacity level gauge for a period of 96 months or 100,000 miles"
That's for the 30 kWH battery.
Keep in mind that Nissan originally didn't offer a battery capacity warranty at all when the 2011/2012 models were still new; I remember signing paperwork that specifically made that clear. It was added in 2013 (and retroactively to earlier Leafs) after the sh--storm that brewed when early Leafs in hot climates began to lose capacity rapidly.
Blue Ocean 2012 Leaf SV, lost that 1st bar at 34 months/26,435 miles. Lease returned 2 months later. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F.
Now driving a 2015 VW eGolf SEL.