My understanding is that once the engine is at the maximum load, the best fuel mixture is pretty stable or flat.
I'm not saying that's always true - just my understanding.
Maybe with low gear ratios in drag racing sometimes that max load doesn't occur until near the top rpms/ end the strip?
Third gear at the big end 1/4 mile slightly leaner for me. 1/8 mile you are not in third very long. With the big swing in AFR; plug reading and mph time. My airgap didn't flow even until I deep ported.