True, but only after revision and correction, which never happened. The fact the Church insists the moral force is maintained to this day shows that nothing has changed. Not only in 1966 but during the reign of Benedict the XVI. You have nothing since do you?
Books on the Index have been removed after revision and correction or, in the case of heliocentrism, because the condemnation of it was lifted by papal decree. Works on the Index do not necessary remain forever on the Index. They may be removed. The Index, therefore, cannot be treated as irreformable and infallible.
When the Church takes a work off the Index, the "moral force" of this decision is that it is OK to read the book. There is no principle of "once on the Index always on the Index."
This is a docuмent which responds to the mistaken idea that now that the Index is dissolved we can read whatever we feel like. That's just wrong. Works on the Index were there for a good reason, usually reasons which still apply. But none of this is relevant to works which the Church has decided to remove from the Index. They were removed for a good reason and we are free to read them.