I agree with what your saying but feel you may have oversimplified it.At the risk of oversimplifying this myself let me add I agree you get more efficient at burning fat at increasingly higher levels of intensity through training but you do this while also using stored carbs (glycogen)the result being the glycogen is spared and it takes longer to deplete.However when it does deplete for well conditioned cyclists with low bodyfat levels particularly a crisis/famine response occurs and the body tends to try to horde remaining fat stores by tearing down muscle/protein for fuel.I'm sure training improves your ability to better utilize both sources and keep going but at lower intensity since these are relatively inefficient fuel sources.As to post training I think the effect your refering to is probably the raised metabolism effect that exercise(the more intense the more effective)has causing you to continue to burn elevated fat levels post exercise(fat is actually a preferred fuel of such low activity resting states).Any increased muscle mass as previously stated raises fat metabolism as well.