Laser-induced breakdown spectroscopy (LIBS) offers rapid bitumen assessment for oil-sand tailings, but wet and dried measurements interrogate materially different targets. The central question is whether a wet target or a dried target provides the stronger analytical margin when low-end detectability, proportional validation error, and loss of the water-bearing matrix are considered in one calculation. Ten tailings samples were evaluated from S1 to S10, with bitumen contents of 0.5, 1.0, 2.0, 2.5, 3.0, 4.0, 4.5, 5.0, 5.5, and 6.0% and water contents of 72.55, 64.86, 62.95, 59.72, 59.24, 54.11, 60.63, 60.01, 61.77, and 61.52%, respectively. These values define a severe hydrated matrix, especially at S1 and S2, where the water/bitumen ratios are 145.10 and 64.86. A Hydration-Gated Detection Margin (HGDM) score was calculated from three explicit quantities: conservative detection reserve based on the upper limit of detection, validation retention based on the mean internal/external relative error, and state integrity based on whether the hydrated sample is preserved. Wet LIBS and dried LIBS have identical internal and external RMSE values of 0.3%, but wet LIBS has a lower mean relative error (6.0% versus 8.4%) and a lower conservative detection boundary (0.5% versus 0.9%). The mean HGDM score is 0.756 for wet LIBS and 0.543 for dried LIBS. Wet LIBS gives the higher score in all ten samples, enters the controlled band at 1.0% bitumen, and enters the strong band at 3.0% bitumen. Dried LIBS remains fragile through 1.0% bitumen, enters the controlled band only at 4.0%, and does not enter the strong band within the 0.5–6.0% range. The direct answer is that wet LIBS is the more defensible process-facing route for hydrated tailings because it preserves the matrix being measured while retaining the stronger low-concentration detection reserve.