There may be a reason to have the direction of the tread specified, but, you can be positive, with a bicycle tire, that it's not for water dispersion.
Because auto tires have tread - in fact, NEED tread, so as to help with hydroplaning, bicycle tire makers seem to feel the need to include tread on their tires, too, as a comfort factor for buyers. There's no reason for tread on road tires, but, the marketing blurbs will say they're there to 'channel water.'
At 50 psi inflation pressure, a smooth, treadless tire can't hydroplane 'till you hit nearly 70 MPH!
The actual formula to calculate the potential speed that a hydroplane condition could exist is:
Speed (in MPH) = 9.72 X the square root of the tire pressure (in psi.)
The higher the air pressure in the tire, the higher the minimum potential hydroplane speed. Note that the only variable involved in this calculation is the air pressure...
If you wanted to rearrange the formula to see what the minimum tire pressure would need to be, if your maximum speed was, let's say, 35mph, it works out to 13 psi.