The book was not on the Index in 1948 (I already mentioned that it was Indexed in 1681, and then subsequently “rehabilitated”);
It was condemned by 102 of 150 doctors of theology at the Sorbonne, and provided the link where this info is contained in the 2nd post of this thread, as well as the reasons for that condemnation;
It was also mentioned in the same first two posts of this thread (which contained links to each article) that not only was the cause for canonization of Mary of Agreda definitely halted because of this book, but also that even Cardinal Ratzinger and the conciliarists take issue with it.
Bishop Tissier de Mallerais also sponsored and endorsed a book in 1993 by a French SSPX priest cautioning the faithful against these books.
If in order to clear the Mystical City, you wish to dispute the veracity of the citations or claims of these authors, please do so.
"Divine Mercy" diaries was condemned and put on the Index in 1959 by the Holy Office whose prelates were appointed by Pope Pius XII.
Poem of Man-God was on the Index from almost day one until anti-pope Montini abolished the Index in the 1960s.
The Mystical City of God was taken off the Index long before Vatican II. This act by Holy Mother Church, de facto, refutes the veracity of the claims of the aforementioned authors, +Lefebvre, et al, in advance.