The guy writing the book doesn't know anything. He's Vatican II, and the only thing you can expect from him naturally would be lies, confusion and deception.
Hence the definition of Baptism of Desire by St. Thomas Aquinas: Forasmuch as someone’s heart is moved by the Holy Ghost to believe in and love God and to repent of his sins, not only without Baptism of Water, but also without Baptism of Blood, one receives the effect of Baptism by the power of the Holy Ghost ( Summa Theologica, [hereafter ST] III, Q.66 A.11).
Aquinas did not believe in such a thing.
St. Thomas Aquinas, Summa Theologiae, Pt. III, Q. 68, A. 2, Reply to Obj. 2: “If therefore a catechumen has the desire for baptism… then such a one departing [or dying] does not immediately attain eternal life but will suffer punishment for past sins. Nevertheless he himself will be saved in this way as though through fire, as stated in 1 Cor. III.”
That was his opinion, and many Saints had different ideas on Baptism of desire. Remember, they didn't have the internet and were often wrong on many things. For example, St Gregory Nazianzien rejected Baptism of desire outright.
Dogmatic definition
Pope St. Leo the Great, dogmatic letter to Flavian, Council of Chalcedon, 451: “Let him heed what the blessed apostle Peter preaches, that sanctification by the Spirit is effected by the sprinkling of Christ’s blood (1 Pet. 1:2); and let him not skip over the same apostle’s words, knowing that you have been redeemed from the empty way of life you inherited from your fathers, not with corruptible gold and silver but by the precious blood of Jesus Christ, as of a lamb without stain or spot (1 Pet. 1:18). Nor should he withstand the testimony of blessed John the apostle: and the blood of Jesus, the Son of God, purifies us from every sin (1 Jn. 1:7); and again, This is the victory which conquers the world, our faith. Who is there who conquers the world save one who believes that Jesus is the Son of God? It is He, Jesus Christ, who has come through water and blood, not in water only, but in water and blood. And because the Spirit is truth, it is the Spirit who testifies. For there are three who give testimony – Spirit and water and blood. And the three are one. (1 Jn. 5:4-8) IN OTHER WORDS, THE SPIRIT OF SANCTIFICATION AND THE BLOOD OF REDEMPTION AND THE WATER OF BAPTISM. THESE THREE ARE ONE AND REMAIN INDIVISIBLE. NONE OF THEM IS SEPARABLE FROM ITS LINK WITH THE OTHERS.”
Pope St. Gelasius, Decretal, 495: “Also the epistle of blessed Leo the Pope to Flavian… if anyone argues concerning the text of this one even in regard to one iota, and does not receive it in all respects reverently, let him be anathema.” (Denz. 165)
Pope Paul III, Council of Trent, Sess. 5, on original sin, ex cathedra: “If anyone asserts that this sin of Adam... is taken away either by the forces of human nature, or by any remedy other than the merit of the one mediator, our Lord Jesus Christ, who has reconciled us to God in his own blood, ‘made unto us justice, sanctification, and redemption’ (1 Cor. 1:30); or if he denies that the merit of Jesus Christ is applied to adults as well as to infants by the sacrament of baptism… let him be anathema.”
So, it's clear that Baptism of water is the only method to save children and men. Since the spirit of THE SPIRIT OF SANCTIFICATION AND THE BLOOD OF REDEMPTION AND THE WATER OF BAPTISM are inseparable.