  Transit Timing Variations (TTVs) can provide useful information on compact
multi-planetary systems observed by transits, by putting constraints on the
masses and eccentricities of the observed planets. This is especially helpful
when the host star is not bright enough for radial velocity follow-up. However,
in the past decades, numerous works have shown that TTV-characterised planets
tend to have a lower densities than RV-characterised planets. Re-analysing 34
Kepler planets in the super-Earth to sub-Neptunes range using the RIVERS
approach, we show that at least part of these discrepancies was due to the way
transit timings were extracted from the light curve, which had a tendency to
under-estimate the TTV amplitudes. We recover robust mass estimates (i.e. low
prior dependency) for 23 of the planets. We compare these planets the
RV-characterised population. A large fraction of these previously had a
surprisingly low density now occupy a place of the mass-radius diagram much
closer to the bulk of the known planets, although a slight shift toward lower
densities remains, which could indicate that the compact multi-planetary
systems characterised by TTVs are indeed composed of planets which are
different from the bulk of the RV-characterised population. These results are
especially important for obtaining an unbiased view of the compact
multi-planetary systems detected by Kepler, TESS, and the upcoming PLATO
mission.
