On the contrary,
The only location that a ABC piston seals the bore is at the top of the stroke. The bore of the cylinder is tapered, being narrower at the top. The piston is "loose" in the bore until the top of the piston reaches the pinch point at the top of the bore. A ringed piston's
ring is in constant contact with the entire length of the bore from top to bottom, which would be in constant friction. The ABC seal at the top of the piston is greater than the seal of a ringed piston, giving you more compression. All of this assumes that the piston to sleeve fit is good on the ABC type and that the piston to bore fit is good on the ringed type.
Also, the internal components of a ABC engine, (sleeve mainly), is made of a different material than that of a ringed engine.

Jesse