The cover has very little to do with the perceived "softness" of the ball, except on the shortest of short game shots and putting. The feeling of softness comes from the compression of the ball, and compression is largely a function of the mantle layer (if there is one) and the core of the ball.

In short, you can't just look at the cover material if you are looking for how a ball will "feel". The cover is a small part, but on full shots, the cover material is only a very small portion of what is felt.