Most orthodox seeds last longest frozen — but some taxa are damaged by −18 °C and survive far better at 5 °C. Detecting that from monitoring data: compute per-species R5 (the longest supported interval at 5 °C) and R18 (at −18 °C), then flag freeze sensitivity by either of two triggers.
The ratio trigger: R18 ⁄ R5 ≤ 0.5 — the frozen interval is at most half the refrigerated one. The ≤ matters; a species whose frozen interval is exactly half was the edge case that forced it. The CI trigger: 5 °C has statistical support (GLM or Wilson) at its latest interval, −18 °C has none, and R5 > R18 — weaker evidence, so it requires both the confidence asymmetry and the raw ordering.
When one storage has no data the flag is NA (you can't compare), with one honest override: if the species' interval demonstrably comes from −18 °C data alone — it survived 20 years frozen — flag FALSE, because the seeds themselves already answered the question. Every flag carries a plain-language reason string; a boolean without its reason is unauditable.