Violin plots of molecular mass ratios for Class I/FS (i < 70^∘; blue) and Class II (gray) disks. Top panel: mass ratios normalized to hot water. Bottom panel: mass ratios normalized to cold water. Individual sources are shown as points, with upper limits indicated by downward-pointing arrows. When normalized to hot water, the ratios of HCN, C₂H₂, and CO₂ are similar between the two classes, but the cold-to-hot-water ratio is elevated in Class I/FS (median ﹩\mathrm{log}({M}_{{\rm{cold}}}/{M}_{{\rm{hot}}})=1.30﹩ vs. 0.63). When normalized to cold water, all ratios are systematically lower in Class I/FS, indicating that the chemical difference is driven by a cold water excess rather than a carbon-species deficit.