This is exactly right and if you think about it, it's also the reason why it doesn't correct for tank height. Some things are still up to the modeller to do correctly . Explaining the physics behind how a uniflow works though is a little more complicated but once it's understood it's a case of smacking the head and saying Dohhh, of course!

The very first use of uniflow was in a CL speed model in the late 40's because those engines are tuned right to the ragged edge and can't afford any change in mixture through the entire flight. The first recorded use in a CL stunt model was in 1960 and they've been used ever since. The heli guys got onto them a few years ago too.