Spitfire IIa prop pitch

[nakedsquirrel]

The Spitfire IIa prop pitch seems to behave differently than any of the other aircraft in game.

Most aircraft will gain some speed with a slightly coarse pitch, but the Spitfire IIa is fastest with the prop pitch set to fully fine.

Is this unintended, or is there something about the Spitfire IIa prop pitch that makes it different from the other aircraft? (IE is it supposed to be a version of auto-pitch?)