Strip engine code set but binary still contains unused engine code

Hi,

I've got "Strip engine code" set and I'm using IL2CPP, but when I examine the symbols from my final binary (i.e. when I download the DSYMs from iTunes Connect) I see things like RakNet and Colliders and physics in there, none of which I use. I'm using Unity 5.4.3f1. Is it not possible to strip these things, or was this improved in a newer version of Unity?

Thanks,
Sam