No, remitting the temporal punishment due for sin differs from the use of economy. Indulgences are built upon the doctrine of merits. This is how one can apply indulgences to the dead per modum suffragii, the Church grants this person the merits associated with the indulgence, and through his prayers, he hopes God will apply those merits to the soul in purgatory. There is no such occurrence with economy. If I were ask my bishop to apply economy to me, and grant me the merit of forty days’ worth of canonical penance, he would look at me as if I had lost my mind, and imagine how much crazier still he would think I was, if I told him that I intended to apply the merit given to me out of economy to one of my deceased relatives or friends per modum suffragii. In this way alone we already know that indulgences differ from the use of economy.
First of all, the mistaken assumption here is that the doctrine of indulgences is part of the dogma of Purgatory, Indulgences are primarily for the satisfaction of penance on
earth. This has ever been its main intention. We can discuss indulgence without referring to Purgatory, which is what I propose we do. If we limit indulgences only in reference to this life, not in the life hereafter, there is a greater relation to economy than you might be willing to admit.
Secondly, the early Church remitted the normal canonical penance due to certain sins because of evidence of the penitent’s good life. HIs good acts were the basis of the indulgence. The indulgence was granted out of economy. That’s the same with the Latin Catholic Church, except that Latin Catholic theology has attached “merit” to each good act. We can talk about indulgences without referring to “merit.” We can even talk about indulgences without calling it “indulgences.”

But the basic assumptions of Latin indulgences is patristic. We don’t need to accept the later Latin accretions (not that those additions are necessarily wrong).
Furthermore, the canonical penance differs from the Latin concept of temporal punishment demanded by the Divine justice. The former is for the transformation of the sinner, and it is dissolved upon death. If one dies while serving penance, it is not held that he must go and complete this penance (or suffer an amount of pain equivalent to it) in a place of purgation, because satisfying the Divine justice is not the purpose which the canonical penance serves.
First of all, I agree with this as an Oriental. However, in the Oriental Tradition (can’t say how strong it is, but it is present), it is possible that even those who have died as sinners, after being punished spiritually after death in Hades, can be transformed. It’s just a possibility that some people hold (a theologoumenon), not saying that it is an actual doctrine of the Oriental Churches.
Secondly, you have a misunderstanding of the Latin concept of Purgatory if you think that it is for “the transformation of the sinner.” There are no sinners in the Latin understanding of Purgatory, since all mortal sin has been forgiven, and there is no possibility for justification (per se) in the afterlife. Purgatory is for the building of holiness that is required by the Divine Justice (according to Latin theology). It is a transformation (a continual transformation in the Eastern understanding), but it is not from the state of being a sinner - only a transformation to more holiness.
Plus, if it were the case that the canonical penance were supposed to satisfy the Divine justice, then how can we be sure that five years of penance is enough for trigamy, or that fifteen years of penance is enough for adultery? Would we really arrogate to ourselves the power to know the demands made by the very justice of God itself (something which St. Isaac of Nineveh teaches is impossible)?
You think the early Fathers were arrogant for assigning a number of years of excommunication to people for certain sins? What is satisfied is the holiness demanded by Divine Justice. The penance leads to holiness and is for that purpose. It is not “pay back.” I have yet to see a single magisterial document from the Latin Church (much less the Catholic Church as a whole) that states that penance is for “pay back.”
Since we reject the thinking that forgiven sins need to be punished, I do not see how temporal punishment, which is demanded by the Divine justice, could in any way be equivalent to the penance.
Brother Vico gave a good explanation of “temporal punishment” in a previous post from the Catechism of the Catholic Church. I think much of the problem is that too many people presume “Divine Justice” means “Divine Vengeance,” Latins and non-Latins alike.
Blessings,
Marduk