Reproduction of Fig. 7 from Thorngren et al. (2016), showing the mass in heavy elements of weakly irradiated transiting giant planets as a function of the total planet mass. Relationship (1) is also illustrated. The magenta curve shows the expected enrichment if one considers the accretion of gas with 1% metallicity and the accretion of planetesimals following Venturini & Helled (2020). The green curve represents the case with a gas metallicity of 30%, the most favorable case expected from Sect. 2.