This is just sort of a guess, I'm not an expert.
It sounds like what is happening is that I think the AC system is designed to run optimally with the AC compressor running at "normal" engine RPM.
But, when you gun the engine, you also momentarily increase the RPM of the AC compressor, because it's driven off the crankshaft pulley via a belt. As a result, the differential pressure across the evaporator expansion valve increases, making the AC system increase it's output.
The expansion valve is usually thermostatically controlled by a capillary sensor the reads the temperature of the evaporator coil and regulates the amount of refrigerant passing through the coil. Like so:
It takes a certain amount of time for the expansion valve to respond to the temperature change in the evaporator coil. Usually that's not a problem at fairly constant RPM. Theoretically, I think if you kept up the high RPM for an extended period, it would give enough time for the expansion valve to compensate.
In other words, the increase in RPM on the AC compressor is almost instantaneous, but the AC system itself has a latency period before it can adjust to the new conditions.
As you observed, it takes a short time for the system to stabilize after you take your foot off the gas. Until it does, the evaporator coil is still colder than normal, until the expansion valve catches up and puts things back to normal. The fog you see is caused by the super-cooled air condensing the ambient water vapour, and then goes away, once the evaporator coil warms up a bit.
If the AC is working fine, like you say, then my guess is it's acting in a way you'd expect and there's no real problem.
Does that make sense, or am I on crack?