Comparison between observations and models in an observational plane: M/R vs. GaiaG magnitudes. Each star is indicated with a different symbol and colour. For each star, its effective temperature has been computed as the average value between the measurements by Cummings et al. (2018) and Gentile Fusillo et al. (2019) and the corresponding models are over-imposed and colour-coded as the corresponding star. All stars lay below the corresponding curves, indicating a discrepancy between the adopted models and our observations.