Those criteria are not indicative of a sequel. For example, Star Wars Episode IV would be considered a sequel by this metric. As would Indiana Jones: The Last Crusade. Meanwhile the first Avengers movie is, if nothing else, a sequel to Thor, Captain America, and Iron Man. Yet it doesn’t count by these criteria.
Those criteria are not indicative of a sequel. For example, Star Wars Episode IV would be considered a sequel by this metric. As would Indiana Jones: The Last Crusade. Meanwhile the first Avengers movie is, if nothing else, a sequel to Thor, Captain America, and Iron Man. Yet it doesn’t count by these criteria.