My understanding of how it works is this

The low speed needle isn't in a fixed position, relitive to the throttle body, like the high speed needle is.
As you add air (throttle body opens) the needle opens also letting in more fuel, so the needle setting (air/fuel ratio) stays consistant wheather your idle opening is at .5mm,.75mm or 1mm.
As you open the throttle the lsn mixture setting is the same, just the volume of both increase.

So yes the mixture changes, they both increase, but the ratio stays the same

Is that the answer you're looking for?