This says it perfectly in regards to BOB and BOD>
Catechism of the Council of Trent, On Baptism - Dispositions for Baptism, Tan Books, p. 180: "INTENTION - ... In the first place they [adults] must desire and intend to receive it…" Thus the mention of the word INTENT for catechuems. The untold number of catechesits who have died throughout the centuries BEFORE receiving Baptism , certainly a number of them have entered purgatory/ Heaven.
Hopefully those 'untold number of catechumens' who have died before receiving the baptism of water in the Catholic Church;they have died without visibly receiving the baptism which they desired, are in Heaven.They could have received the baptism of water in a manner known only to God ( Aquinas/Xavier).
However you are mentioning this with reference to the dogma extra ecclesiam nulla salus (EENS).If you were simply talking about a hypothetical isolated case it would not be an issue.
For a case of the catechumen to be an exception to all needing to be incorporated into the Catholic Church as a member, the person must exist.We need an actual person in the present times for there to be an exception.
There is no such person and there cannot be any such person for us human beings.Why?
For example let us suppose one of these 'untold number of catechumens', who is mentioned above was known to a Mr.X. Mr.X cannot say ,"Look this catechumen who died yesterday without the baptism of water and has been buried in the Church today, is an exception to the dogma extra ecclesiam nulla salus. Since he has gone to Heaven without the baptism of water in the Catholic Church." Mr.X does not know if the catechuman was in Heaven without the baptism of water.
Since this would be a personal case, judged and known only to God.
He would not know if God chose to give the catechumen the baptism of water after he died.So the deceased catechumen is not really an exception to the dogma EENS.
Mr. XYZ would not know if the person committed a mortal sin and so is not in Heaven.
Neither can he say that all people in general do not need the baptism of water in the Catholic Church, since there are known exceptions, like this particular catechumen.This case is not a known exception.
He cannot say that most people are saved since this catechumen whom he knew has been given a burial in the Church.We know that most people in general are on the way to Hell without faith and the baptism of water(AG 7, LG 14).
Mr.X cannot assume that there could be a baptized Christian who will go to Heaven even though he is not baptised in the Catholic Church and as an adult did not have Catholic faith.Christians in general are on the way to Hell according to the Catholic Church(AG 7, LG 14, EENS etc).
The general way of salvation for adults is Catholic Faith which includes the moral and faith teachings and the Sacraments.
It cannot be said that since a catechumen has died and has been given a Catholic burial ( since it is assumed by the cardinals and bishops that he will be saved as such ) the baptism of desire is a known case without the baptism of water.The cardinal and bishops cannot say that any particular catechumen is there in Heaven without the baptism of water in the Catholic Church.
It cannot be assumed that this is a case which is an exception to all needing to be incorporated into the Church and so the majority of people can be saved and will be saved in a form of universal salvation.
The ordinary means of salvation is being a member of the Catholic Church.The general means of salvation is not being saved since there was a desire for the baptism of water.
We cannot say that there is known person who desired to enter the Church and had a good conscience and so is to be given a burial since the person is saved.Faith and baptism are the general means of salvation and not assuming that someone is saved with a good conscience.
The catechumen is technically outside the Church he is on the way to Hell. It is only with good will and the new theology based on invisible cases being visible that he is given a burial.
For example a person who commits suicide is on the way to Hell but there are liberal bishops who will still given him a burial.
Presently there are people living in manifest mortal sin and bishops will allow them to be buried as Catholics.
The bishops in Malta and Germany will give the Eucharist, and I assume a burial too, to Catholics who have divorced and remarried.
Similarly there are Protestants and non Christians who are outside the Church and pastorally bishops will permit them to marry Catholics and not consider it adultery.