Gs come from acceleration, either straight line or centripetal. I don't think there is enough control authority in starship's fins to create much centripetal ac

Gs come from acceleration, either straight line or centripetal. I don't think there is enough control authority in starship's fins to create much centripetal acceleration the way a fighter jet's wings can. If the rocket is capable of it, it would do the same whether it was belly-flopping or dropping straight down the whole way. Any passengers will certainly get an inner-ear workout, but I can't imagine how the flip, more or less around the rocket's own axis, could contribute significantly to G-loading.