Most area lighting isn't going to use bleeding-edge LED's for two reasons: lumens/$, and thermal/electrical ruggedness.
Relative to lower-performing LED's, bleeding-edge products have a price premium. Flashlight and specialty luminaire manufacturers will pay this premium, but area lighting manufacturers have to compete against florescent and arc lamps' lower cost of acquisition, and similar lumens/watt, and (generally better) lumens/package performance. They will prefer older-generation LED's due to their lower cost per unit and better price/performance ratio.
Another plus of older-generation LED's is maturity, which leads to more robust thermal and electrical performance - LED manufacturers have had time to further improve processes for existing technology so its previousl bleeding-edge performance isn't stressing the parts so hard. Another aspect of product maturity is better consistency and availability: if you want something particular - ie >100lm / 3.2V@350mA / 4200K CCT / with a <0.25% failure rate after 10,000 hours / all @ 75C junction temp - by the container load monthly, it's easier to get that from an established product than a new one.
. The XM-L is a nice bright efficient LED to design with but I wouldn't call it the brightest, as companys like Bridgelux and Edison Opto have the array leds that emit in the 4000lm range.
