It should stop in either direction as the adjuster plate reaches it's limit.
At the upper end, it reaches it's physical limit, and at the lower end it contacts the stopper ring.
That black fork pre-load adjuster fits over flats on the adjust case, which is part of the cartridge assembly.
If you use excessive force, you could round off either the adjuster nut, the adjust case flats, or both.
What you can do is remove the retaining clip holding the adjuster nut onto the adjust case (middle photo), and remove that adjuster nut to check if it or the adjust case (lower photo) have been rounded off.
And also, never use excessive force to adjust the rebound adjuster.
I only use the tips of my finger with a smaller screwdriver (tweaker) to make adjustments.
If too much force is used, the rebound needle and/or seat can be damaged or destroyed.