Your theory would be correct except you can’t assess ring seal without pressure.
The rings do not seal based on radial tension.
All piston rings are gas operated. They require combustion pressure to get down past the top of the piston to the top of the ring. Then that pressure goes across the top of the ring to the space behind the ring and that pressure forces the the ring to the cylinder wall and causes the seal.
Plus we need to remember that engine oil is the gasket that seals the rings.
Testing without pressure doesn’t mean much if anything.