Actually mounting a missile pointed slightly downward is very common. I have seen so many photos on all air forces, Eastern bloc, western bloc, neutral countries etc.It shouldn't be pointing downwards for it'll have a very adverse effect on aerodynamics during flight. If as you said there's no camera effect, then you have to say that the LT-2 and PL-8 (to a slighter extent due to its shorter length and therefore its depth of field) are mounted pointing downwards too.
I am not engineer so I cannot comment on the technical aspects, but my layman's guess is that it actually provides lifts as in the same effect as aero-foil, though in cylinder form instead of a wing shape, the lift generated could be to off-set against the weight of the missile. My 2 cents. though I could be wrong.
Notice the wing tip missile is pointing downward?