Remark: What this improves, and what it does not

Lemma lem:record-marginal uses $s$ fresh record qubits and requires $n+s\le N$. I's budgeted stability theorem uses whole-register records, including further records of intermediate deferred states; its displayed conditions include $2n\le N$ and $2(n+s)\le N$ I (label thm:stability). The budgets price different comparisons. The present exact marginal argument does not remove any register from that approximate continuation theorem, nor does it supply an approximate update estimate.