Correct. In order for the former to work you'd need to establish a POD in which the union between Brazil and Portugal lasts longer. Your best bet in that reguard is for the Constitutionalists to moderate on their centralizing tendencies and maintain Brazil's separate legal entity status within the grander Imperial structure rather than trying to impose direct rule from Lisbon. Over the next few decades, their legal structures would increasing diverge as conservative policies were adopted by Rio and liberalism gains ground in Portugal, followed by increasing dependence of the government in Lisbon on revenue extracted from the colonial plantations. Eventually, the taxation vs. representation situation breaks out into a crisis (Maybe there's a push for expanding the franchise without changing the tax structure, or calls for land reforms in Portugal proper?) to the point the nobility, church, ect. end up victims of a mass confiscation of their property in Portugal proper (Similar to the dissolution of the monasteries in Spain), from which they retreat to Brazil.