The same St. Peter in the same book contradicts you magnificently.
For when the Prince of the Apostles was proclaiming the Gospel, it is recorded by St. Luke,
To him all the prophets give testimony, that by his name all receive remission of sins, who believe in him.  While Peter was yet speaking these words, the Holy Ghost fell on all them that heard the word.  And the faithful of the circumcision, who came with Peter, were astonished, for that the grace of the Holy Ghost was poured out upon the Gentiles also.
 For they heard them speaking with tongues, and magnifying God.  Then Peter answered: Can any man forbid water, that these should not be baptized, who have received the Holy Ghost, as well as we?
So St. Peter himself, wonderfully illumined by God, refutes the pharisaic errors of the present time, by asserting authoritatively, that these unbaptized catechumens have received the Holy Ghost just as the baptized disciples had. And he had preached the Trinity, Incarnation, Passion and Resurrection, but had not yet mentioned baptism, so the desire for baptism was only implicit in these catechumens.
Hence, St. Augustine, "I do not hesitate to put the Catholic catechumen, burning with divine love, before a baptized heretic. Even within the Catholic Church herself we put the good catechumen ahead of the wicked baptized person . . . For Cornelius, even before his baptism, was filled up with the Holy Spirit [Acts 10:44–48], while Simon [Magus], even after his baptism, was puffed up with an unclean spirit [Acts 8:13–19]"
So also St. Thomas, "So also before Baptism Cornelius and others like him receive grace and virtues through their faith in Christ and their desire for Baptism, implicit or explicit"
So the clear testimony of the Holy Ghost, speaking through the Prince and head of the Apostles, in inspired Scripture as divine revelation strictly so called, with patristic Tradition and testimony confirming, is that the sacramental effect of baptism, just like penance, can be received in desire, which no one can lawfully call into question.