WOT-Wide Open Throttle and high-rpms is when the most air is sucked into engine. This places highest compression-pressure inside cylinders. And generates most pressure and heat when mixture is ignited.
This condition is most ripe for pinging/knocking/detonation to occur after spark ignites mixture (pre-ignition is something completely different). Under high-pressure and heat of WOT conditions, intermediate combustion compounds forms. One of these types, radical alkyl groups, are extremely heat & shock sensitive and will auto-ignite on their own. This creates a 2nd flame-front somewhere else in combustion chamber. This 2nd flame-front collides with original one and generates an extremely high-pressure & high-temperature spot in combustion chamber. This collision is heard as an audible pings, similar to shaking popcorn kernels in tin can. If engine is operated under this condition for long, detonation & pinging can burn holes into piston tops and melt valves.
So... even though highest-efficiency occurs at 14.7:1 AFR-air fuel ratio, and is what ECU tries to maintain under partial-throttle operation with O2-sensor feedback (max-power usually occurs around 13.5:1 AFR). However, under high-load 80-100% those AFRs are too hot for most engines tuned for 87-oct. pump petrol. So... pretty much ALL bike manufacturers program ECU to turn off O2-sensor feedback operation under high-load and go with richer 10:1 to 12:1 mixture, which is about 25-30% more petrol (per air-mass) than lower-load operation.
This higher-fuel richer mixture burns cooler, generates a little less power than 14.7:1, but is much more resistant to detonation & knocking. Also if you get bad petrol, or ride in super-hot day, this places engine closer to edge of detonation/knocking. Thus, the pre-programmed high-load zones in factory maps tend to be very rich with extra fuel for safety. Carbs tends to be tuned even richer under WOT than EFI systems.
If you're racing your bike, and can control conditions such as using high-octane petrol (which tends to have more knock-resistant aromatic compounds) and adding extra cooling with larger radiator, you can typically get +5-10% more power by leaning out high-load WOT mixtures. Along with adding couple degrees extra ignition advance.
Anyone remember that '60s hot-rod saying?