Try looking at the dynamics of the interactions, not the parts sitting idle in seperate piles. Cylinder walls distort. The rings have to follow the wall surface and seal on the wall and the ring lands. The face of the compression ring is rounded to seal the bore. The sides of the ring and piston ring lands are flat. As the walls flex, the piston can move more, both in the middle of the stroke where sealing isnt a big deal ,and the top of the stroke where the skirt is 2" down and the rings have to seal as the piston reverses direction. The ring ends up having to slide in and out, and twist all as the piston moves. Once wear there starts, the ring can move more, and the sealing goes away faster. No contradiction. You have to have a stable piston, a stable wall, and a stable ring to keep the sealing affect at it's best.
I'm just stating what I believe. You can remain unconvinced. It's your engine...lol. I have a couple that are approaching 15K. they run fine, make plenty of power, etc. But, I also know of many others that don't go that far before they start showing leak down numbers closer to 10-12%. I think that's high for the mileage. Not fatal, but definately shows faster wear. These are not trailer queens, don't have overdrives, and are raced, so maybe that's it. I'm also sure that like anything else, things like machining quality and assembly quality need to be better for anything to last, and maybe it's the marginal ones that begin to lose seal earlier. It makes sense. The closer one is "to the edge" the more precise the steps have to be.
In regard to GT's car... He's had OD in it for years, and last he and I spoke, IIRC, it was last year and we discussed some top end ideas for a new engine he was working on. It's not like he's changing oil and planning on it living for another 5 years.
PS - Don't confuse a modern casting aluminum/iron liner block with anything designed in the 50s or 60s and cast from aluminum. That's a big mistake.
