I suppose I don't consider that samatha = jhana; it's something I consider in terms of vipassana-samatha.
developing samatha --> developing citta --> fading of passion
developing vipassana --> enhanced panna --> fading of ignorance
Strictly speaking, this would suggest that a samatha integrous with the Dhamma leads naturally away from passion, which means that it has a natural velocity of renuniation, which is an aspect of sammasankappa - 'right intention'.
Jhana is how sensuality finally stops being a draw (MN 14); samatha is necessarily engaged prior to this.