A ship is its flag not its cargo, admiralty law. If the Ukies don’t want the Russkies then the Russkies have no standing in law. The final vote may come down to who actully owns the vessel. If it’s a private company in Ukraine than the company has the call. If it’s a Russkie company flagging its ships with Ukrianian registry because of better port facilities than the owners can accept or refuse help as they wish.
you are no doubt correct...however I believe that the russians don’t want 33 of their battle tanks and spares getting pirated and ending up who knows where - especially if they haven’t been paid for.