For tractors, with very prominent lugs, the theory is that the point of the "V" hits first, then any mud gets squeezed out the V, thus improving traction. Installing them backwards, and it would tend to force the mud towards the center of the tire.

In theory, the same would be true on a bike, whether it is pushing mud out of the way, or pushing water out of the way.

For a lay-person, it is hard to make a good 1:1 comparison between tires as several factors change. I've found that Schwalbe Marathon Plus tires with a prominent tread tend to be quite grippy, but they also use a softer tread compound than say a Gator Hardshell, and thus also wear quicker.