Stones used for sharpening tend to have more, and deeper scratches, and they are generally more central. Sometimes they have a single deep "V"-shaped groove.
This stone matches the world-wide pattern you find with non-sharpening (i.e., ceremonial, counting, etc.) stones.
Check out a book title "Patterns that Connect: Social Symbolism in Ancient & Tribal Art" by Schuster and Carpenter for illustrations.
Whew! I was hoping you'd step forward and answer that one, lol.