Policy optimization (PO) is widely used to post-train language models for reasoning, often with a rigid <think><answer> format. We study what PO learns when this constraint is relaxed. We evaluate a relaxed reward across six models and four benchmarks, then audit learned formats on GSM8K and controlled variants across three on-policy algorithms. In these audits, accepting either explicit reasoning or a direct answer pushes the policy toward the shortest valid format: an <answer>-only response. On GSM8K, the collapsed Qwen-2.5 7B policy produces answer-only outputs in 98.6% of generations and loses 7.1 pass@5 points relative to a strict-format baseline. Controlled rewards show this is not a regex artifact: with nested formats, PO learns easy requirements before harder ones despite a 4× hard-format reward; with mutually exclusive equal-reward formats, the audited Qwen-2.5 7B final policy assigns more than 99% of generations to the easiest format. A sample-gated gradient account fits the pattern: formats receive positive updates only when sampled, so early support can outweigh reward scale. KL-controlled runs show collapse appears only when the policy can move far enough from initialization. The result identifies a practical failure mode for RLVR reward design.