MESA models of post-RGB stars with a core mass of 0.40 M_⊙ and initial accretion rates of 5 × 10⁻⁹ M_⊙ yr⁻¹ (upper panel) and 5 × 10⁻⁸ M_⊙ yr⁻¹ (lower panel). Curves with different colours represent different starting temperatures, while linestyles distinguish different disc masses. Units of M_d and T₀ are M_⊙ and K, respectively. Observations for stars with L <  2500 L_⊙ are shown as symbols, where similar to Fig. 4 non-depleted objects are blue circles, plateau-type objects are yellow triangles, and saturated objects are red crosses. Objects with uncertain depletion patterns are denoted by green squares. If a star does not have a Zn measurement, S is used instead, while if a star does not have a Ti measurement, we used Sc or Fe to plot the [Zn/Ti] ratio (Table A.1).