"This faith conformable to Apostolic tradition catechumens ask of the Church before the sacrament of baptism." Seems to indicate that whatever faith they have is different in the supernatural order than those who receive the sacrament.
"For the completion on the salutary doctrine on justification...it seemed proper to deal with the most holy sacraments of the Church, through which all true justice either begins (baptism), or having begun is increased (other sacraments), or being lost is restored (penance)."
It appears there is no true justification outside the sacraments, and none that is initial without the sacrament of baptism.
Well said. What you speak of as the pre-Baptismal faith, is referred to by theologians as the
fides initialis, a natural analogue to true supernatural faith, but still on the natural order. It is only with the Sacrament that the true supernatural virtue of faith is infused into the soul, which is why the catechumen is asking for faith at the beginning of the Baptismal Rite, despite already having a certain kind of faith that led to his requesting to receive the Sacrament. That is why the Church never considered catechumens to be among "the faithful" ... even if they said they agreed with or "believed" (naturally) everything that the Church teaches.
Catechumens are a bit tricky in that they are certainly not enemies of God, and can be considered to be in an analogous state as the Old Testament just, for whom whatever faith they had was also in an inchoate state, since they didn't know about what Our Lord would actually reveal. Catechumens have ONE of the characteristics of membership in the Church, in that they publicly PROFESS the faith. St. Robert Bellarmine held that the outward profession alone was the characteristic of membership in this regard (so that, for instance, secret heretics who did not have the supernatural faith were still regarded as members due to their outward profession).