As I have said elsewhere, reducing pumping losses are one of the goals of open throttle acceleration. The reason 80% throttle is recommended instead of 100% is that normally 80% keeps the ECU in closed loop mode where 100% takes it into open loop territory, which disregards the O2 sensor. It is a bit like the extra spurt of fuel that full throttle on a carburettor engine gives, derived from the accelerator pump.