1257 The Lord himself affirms that Baptism is necessary for salvation.59 He also commands his disciples to proclaim the Gospel to all nations and to baptize them.60 Baptism is necessary for salvation for those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament.61
The Church does not know of any means other than Baptism that assures entry into eternal beatitude; this is why she takes care not to neglect the mission she has received from the Lord to see that all who can be baptized are “reborn of water and the Spirit.”
God has bound salvation to the sacrament of Baptism, but he himself is not bound by his sacraments.
To tell you the truth I don’t understand how we only know that baptism is necessary for salvation
and that it may not always be necessary.
I have no theory or know of one that can reconcile these two seemingly contrary positions. I have to submit my understanding to the Church on this one. The CCC seems to say that desire and blood are the same but there needs to be a lot of theological discussion on how to reconcile that.
There is a tradition for the desire and blood position and a tradition that seems to opposes it . Like the debate on the Immaculate Conception, I have to accept on faith the prevalent understanding, which is in the CCC. Until, if ever, it is cleared-up by a solemn definition.
Though from what I have read the tradition that says that desire as enough for salvation was always limited to only catechumens.
1249 Catechumens "are already joined to the Church, they are already of the household of Christ, and are quite frequently already living a life of faith, hope, and charity."48 "With love and solicitude mother Church already embraces them as her own."49
I have to make an act of Faith, and that God will clear this up and/or I may never understand it.