Block drafters propose several tokens in one forward pass, before earlier target tokens are realised. Their rejection mixes two losses: missing within-block path information and imperfect modelling of observable information. Accepted length cannot distinguish them. We separate the two with an information floor, the minimum expected rejection at a specified conditioning order; rejection above this floor is the model gap. Estimating both from target rollouts across four domains, four open-weight targets, and a frontier API target yields three findings. First, the all-parallel floor reaches
0.286 at the final slot on Qwen3-4B, limiting even the best proposal to
71% per-slot acceptance. Second, one realised token removes
86--
100% of this floor, a locality also recovered by an independent mutual-information analysis. Third, current drafters remain far above their floors: the final-slot model gap accounts for
43--
64% of DFlash rejection and
85--
92% of DSpark's oracle-conditioned rejection. These findings separate the value of short-range conditioning from proposal quality.