RLBROBST
The spring I'm talking about is located inside the carb behind the rotor and loads the rotor OUTWARD not inward.
This is a very common set up and is used by most manufactures. My guess is that the .40 carb is identical to the .47 and if you remove the screw in the top of the carb and slide the rotor out you will find the spring hiding in there.

I have seen other brands with similar end float, but as I stated before it shouldn't be a problem because of the spring. The only way I can see the end float causing concern would be if the throttle linkage in the model was badly misaligned and was pushing the rotor in against the spring. This could possibly, I suppose, create a condition where the rotor might oscillate in and out. If the movement is only .0015 to .0025 I doubt that it would be an issue.