What is the history of the term "state of perfection" before, during, and after Vatican II? Traditionally, Catholics used language of "state of perfection" (as we can for example read in Aquinas). Why did not Vatican II use this term? What is the history of the term "state of perfection" before, during, and after Vatican II?
“state of perfection” in Vatican II's
preparatory documents
Vatican II's preparatory commission drafted two documents related to religious perfection:

De statibus perfectionis adquirendæ (On the states for acquiring [evangelical] perfection), 15 June 1962
De Ecclesia [On the Church] ch. 5 &quot;De statibus evangeliciæ acquirendæ perfectionis&quot;, 1 December 1962(English translation PDF pp. 21-23)

council interventions
from Fr. Ralph Wiltgen, S.V.D.'s Inside Story of Vatican II ch. &quot;The Second Session&quot;, § &quot;Religious Orders and the Universal Vocation to Sanctity&quot;:

The position of the European alliance was based on the arguments advanced by Father Rahner and Monsignor Philips, and submitted to the German-speaking Fathers meeting in Munich in February, 1963. Those arguments were that the inclusion of the chapter on the religious life would “confirm Protestants in their objections, namely, that in the Church, through the religious state, there exist two essentially diverse paths to salvation; that the laity are not called to evangelical perfection and automatically are always on a lower level of sanctity; and that those who are members of religious orders are automatically considered better than those who are joined in marriage.”

promulgated documents
Lumen Gentium
Chapter 5 of Vatican II's 21 November 1964 dogmatic constitution on the Church, Lumen Gentium, is on the religious, and, although it includes the phrase &quot;religious state&quot;

From the point of view of the divine and hierarchical structure of the Church, the religious state of life is not an intermediate state between the clerical and lay states. […] the religious state, whose purpose is to free its members from earthly cares, more fully manifests to all believers the presence of heavenly goods already possessed here below.

it does not use the phrase &quot;state of perfection&quot;:

religious families give their members the support of a more firm stability in their way of life and a proven doctrine of acquiring perfection. […] The importance of the profession of the evangelical counsels is seen in the fact that it fosters the perfection of love of God and love of neighbor in an outstanding manner and that this profession is strengthened by vows.

Perfectæ caritatis
The 28 October 1965 decree Perfectæ caritatis (PC) dealt with the &quot;adaptation and renewal of religious life&quot;.
The Little Catechism of the Second Vatican Council part 8 notes the following innovations in PC:

&quot;Whereas the old 1917 code* divided people into three categories (clerics, religious, laity), the new code of 1983** – applying Vatican II – divides the « People of God » (sic) into three groups ordered thus: the faithful of Christ, the hierarchical constitution of the Church, and the institutes of consecrated life (in which the religious are diluted).&quot;*can. 107: &quot;By divine institution there are in the Church clerics distinct from laity, although not all clerics [possess orders that] are of divine institution; either of them can be religious.&quot; (commentary)**can. 207: &quot;§1. By divine institution, there are among the Christian faithful in the Church sacred ministers who in law are also called clerics; the other members of the Christian faithful are called lay persons. §2. There are members of the Christian faithful from both these groups who, through the profession of the evangelical counsels by means of vows or other sacred bonds recognized and sanctioned by the Church, are consecrated to God in their own special way and contribute to the salvific mission of the Church; although their state does not belong to the hierarchical structure of the Church, it nevertheless belongs to its life and holiness.&quot;

PC §15 &quot;erases the hierarchy […] between the lay religious and choir religious&quot;:That all the members be more closely knit by the bond of brotherly love, those who are called lay-brothers, assistants, or some similar name should be drawn closely in to the life and work of the community.  Unless conditions really suggest something else, care should be taken that there be only one class of Sisters in communities of women.