I have some smart objects which appear in several artboards within the same document. Editing them doesn't change all the instances where the smart object is used, only the ones within the artboard where the smart object that I edited is sitting.
Same issue happening with version 23.5. This is a bug with certain versions of Photoshop and should be remedied for the price we're paying for a subscription. As a user, having to keep track of linked files to update smart objects across multiple artboards is a pain and feels like laziness on behalf of Adobe's dev team and QA team. As a user, you should be able to have the smart object embeded in the artboards.