> Emissions are tested on a standardized driving cycle that doesn't include full-throttle acceleration

Depends on the car. See Supplemental Federal Test Procedure US06[0], required by the EPA for light-duty vehicle certification since 2007.

It is also largely irrelevant in the real world: nobody is going to tune a car to have mediocre part-throttle performance but then go all-out on full-throttle.

0 - https://www.epa.gov/vehicle-and-fuel-emissions-testing/dynam...