You bring up an excellent point. Symmetry is a key issue on a striker, evident as to the contact point on the materials used, whether or not you get good consistent contact will determine whether or not you get good consistent sound.
If you notice most store bought strikers are flat, they intend on YOU the BUYER to finish the striker to YOUR liking, it is mostly the custom call maker who will take the time to get a good complete symmetric radius on the tip. I most always do this, sometimes the eye may be off a little, but most of the time I try to help the new owner out as much as I can.
As far as keeping it that way, it would be up to the owner to use some sandpaper and a little time, as with all aspects of using a call, maintenance is important.
As for the "graining" issue, look at it like this, where the bite occurs is between the surface of both materials coming together, if one is slick, the other will give. If they both are matched for friction then they both will react accordingly, so it does make a difference as to the grain being oriented in a way that will provide the maximum friction, since the contact area is so small. But does this dictate the entire worth of a striker, no....because the radius being symmetric will allow you as the user to determine the proper angle and amount of pressure applied to accommodate the "influence of bite" ... but...remember the theory of friction, this is why when I run a pot, I check for grain orientation, running the striker with the grain horizontally will produce better friction. More friction. less effort to produce sound, less effort means more opportunity to venture out from the sweet spot in order to broaden the workability of a call...
