The reason why 60fps isnt enabled on some Samsung devices is due to a GPU driver issue that our team and Samsung are continuing to work on. At one point we had a trello card up called "Forced 30fps on Samsung devices" and gave a list of affected devices. Due to trying to keep the trello board updated as often as we can with newer issues we choose to archive the card.
As I said, we are still looking to work on enabling 60fps for as many devices as we can, but we need to balance performance and stability the best we can.