Note everywhere you would expect the council to just slam it's fist down and identify....the metaphysically necessary administration of sacramental baptism as the only route of justification, it does something else.
CANON II.-If any one saith, that
true and natural water is not of necessity for baptism, and, on that account,
wrests, to some sort of metaphor, those words of our Lord Jesus Christ; Unless a man be born again of water and the Holy Ghost; let him be anathema.
CANON V.-If any one saith, that baptism is free, that is, not necessary unto salvation; let him be anathema.
It is not done out of the assumption that catechumens cannot have supernatural faith. The Council says they can.
Catechism 101. Baptism gives supernatural Faith, which one can only receive once. Once one has supernatural Faith, they will always have it. Therefore a catechumen cannot have supernatural Faith both BEFORE and AFTER baptism. It makes no sense.