It has more to do with the refactoring of the NewGameCallHandler they did a while ago. Left-hand or right-hand ought to be irrelevant in the game.
radiant.entities.turn_to(banner_entity, 180) - no matter what you do, the banner will always be placed in the same direction. The rotation of the ghost entity is completely ignored, although fixing this could be easy, given that stonehearth.selection:select_location():use_ghost_entity_cursor 'stonehearth:camp_standard_ghost':done(function (selector, location, rotation) implies that the rotation is passed by the library - it’s just not used.
I could try to add this into Jelly’s NewGameCallHandler override I guess.