Drive direction on tyers..

[mickle]

On the top of the tyre.

Ya.

 

[Mr Pig]

It is so that the cheverons are self cleaning of mud. If the cheveron was the wrong way then mud would be forced towards the centre of the tread pattern clogging the tread.
Look at the back tyres on a farm tractor.

This is what I assumed. The chevrons are designed to push water, grit, mud and debris out to the sides rather than towards the centre of the tyre. I doubt it would make very much difference on a bicycle but it seems obtuse not to fit them correctly.