My house has a few half round corner shelves, in pine. The shelves appear to be from two to three edge joined boards and are quarter sawn. On the underneath is a shallow groove running from 1/2 way down one straight edge across to the same place on the other straight edge. Now it occurs to me that this might be to prevent cupping, except that grooves to prevent cupping usually run with the grain. Is my surmise correct, and if so why across the grain, and why in quarter sawn? Just curious.
Peter