init_atomic_updates calls atomic_updates which builds a Modifier hash of atomic operations by calling various operations depending on the update (set, pull, etc). Most of these operations will call set_conflict to ensure that there are no conflicts between between the current operation and another set operation, but unset does not call it at all. I think it should call it because an unset could be unsetting a field within another field that is set, and thereby cause a conflict. For instance, I should never get this when I call
init_atomic_updates and I can, which causes an error when attempting to apply the updates: {"set" => {"a" => [

]}, "unset" => {"a.0.b" => true}}