Detailed retrieval results for HAT-P-2 b. This planet is part of the group of planets for which the ’FRECKLL-only’ retrieval test depicted a bimodal distribution for the metallicity. Therefore, we carried additional tests: we tested the effect of FRECKLL and the effect of FRECKLL plus TiO, VO, and both TiO and VO on two priors for the metallicity (one on the subsolar side log(Z) < 0, and another one on the supersolar side log(Z) > 0). The upper row presents (from left to right) the fitting spectra for each retrieval configuration tested through this population study, the retrieved temperature profile, and the chemical structure of the planet for the ’FRECKLL-only’ retrieval. The lower row presents the posterior for each test, as normalised distribution.