Yes there is. The circlip opening should be either at the top or bottom. The reason is even though it's small the clip has mass. If the clip opening was at the sides when the piston stops at either the top or bottom of its stroke the clip will want to keeping moving (a body in motion wants to stay in motion)..it could possibly compress and come out of the groove.
I have been involved in mechanics and motorcycling from a young age. I formed Cycle Improvements in 1981 and still have the same passion to learn today as when I started. Hope you find this blog interesting and educational.