Compression and leak down tests are both good so I doubt it's the rings. Exhaust valves staying open when they shouldn't will also cause pressure to leak past the valve seals.
So if the exhaust valves are open, how come the two tests are good? My point is, you're missing something. Pressure will leak out the rings, or out the valves, or both. You will have evidence of the leakage. The valves are not leaking. Pressure is pushing oil out. So it's rings. Just is what it is.
