DM-only versus hydro-simulation-estimated sparsities s_200, 500 (left panels), s_500, 1000 (central panels) and s_1000, 2500 (right panels) for the clusters in the GIZMO-SIMBA (top panels), GADGET-X (central panels), and GADGET-MUSIC (bottom panels) catalogues at z = 0, respectively. The blue squares represent clusters from the full samples, while the yellow triangles corresponds to the relaxed systems as defined in Sec. 2.2. The size of the data points is proportional to mass M₂₀₀ of each cluster from the DM-only simulation. The diagonal line represents the ideal case with no bias, while the shaded areas correspond to 10% (yellow band) and 50% (light-blue band) deviation respectively.