The structure I created is a parallel beam flexure, but with really thick beams. A proper version of that would have thinner top and bottom beams, but keep the small block at the end. It would be incorrect to cut this structure in half to remove the right side. The full length of the beam is required to correctly represent the stiffness of the flexure. If you wanted to minimize node count, you would replace the solid body with two surfaces and mesh with shell elements. These could be bonded or node merged to a small block meshed with solid elements where the surface overlaps the end of the small block.
If instead of a small block at the end, there was a large stiff block of material, it would be appropriate to cut off that large stiff block at the plane where the current small block ends and use a Remote Force using a Rigid behavior.