Distribution of stars identified as RGB or AGB, with log(g) < 2.2 (stars above the main RC population in a Kiel diagram) as a function of ΔT_ref (in blue). The dot-dashed red line shows a Gaussian fit of width 44.04 K centered on −26.40 following the distribution of α-rich stars. The orange dashed line indicates the two-σ limit of the measured RGB sample distribution following Section 5.