Just my opinion ...
That doesn't look like an abrading stone. It might be a round piece of sandstone with plow scars on it, but abrading stones that I know are small and not that big. You use an abrading stone in flint knapping to set up your platforms for striking. They would have to be much smaller than that.
Also, if it were used for making implements like axes, celts, etc ... it would probably need to be a flat piece of stone. A curved stone wouldn't be economical for making a celt or axe. You need to be able to push and pull the piece across a flat surface several times. Not over a curved surface.