Step 3 variance (N=10) showed mean depth 3.9 (vs step-2's 7.1). Confound: step-3 used 3 generations vs step-2's 5. Cannot distinguish whether depth drop is from (a) fewer generations or (b) substrate competition for proposal bandwidth. This control: matched 5 generations × 20 rounds (same as step-2). Same engine with CA substrate. If depth ~7 returns → drop was generation-count. If depth stays ~3-4 → CA competition genuinely shifts the program. Pre-registered: - GENERATION-COUNT hypothesis: depth ~6-8 (matches step-2 range) - SUBSTRATE-COMPETITION hypothesis: depth ~3-5 (matches step-3 N=12) - Either result is informative. Also tracking: do CA-axis acceptance share and reasoning grounding stay ~70% / ~100% with longer runs?