Similar to some of the others, I've lost count how many sets of KO2s I've had, from pickups, to SUVs, to Suburbans. And now, my JK. I have yet to have one fail on me. The KOs, rated as a 60,000 mile tire, is what I've gotten with them. The set on my Suburban, took right to 59K. Wasn't to the wear bars yet but, with the rocks/etc making regular contact with the tire's carcass, decided it was time.
I suspect what,'...a few people...' have meant by no tread warranty is that, unlike the KO, the KO2 has no mileage warranty. Many of the BFG tires that used to have mileage warranties, no longer do. If you go to bfgoodrichtires.com, you can download their 24 pg warranty guide.
All BFGoodrich® tires have a Standard Manufacturer's Limited Warranty, which covers defects in workmanship and materials for the life of the original usable tread, or for 6 years from date of purchase, whichever occurs first. 'Usable tread,' is defined as 2/32nds...across the face of the tread. They define uneven wear as a tread groove difference of 2/32" inch or more across the face of the tread on the same tire.
Read the entire warranty, there is no requirement that the tire be an OEM fitment. Only that it applies to the vehicle to which it was originally fitted. It's a basic 'manufacturer' warranty against manufacturing defects. Not warranted are, "cuts, snags, bruises, impact damage or punctures," they say.
There's a lot of discussion about how to make a claim. PIA. Far easier, as many do, to simply buy a certificate from Discount Tire. If 'anything' happens to it during it's life, you're golden.
...as for on my JK, couldn't be happier. Dramatically better than what they replaced.
