Simple: only a minority in the PCA are really comfortable with this:

Q. 76. What is repentance unto life?
A. Repentance unto life is a saving grace, wrought in the heart of a sinner by the Spirit and Word of God, whereby, out of the sight and sense, not only of the danger, but also of the filthiness and odiousness of his sins, and upon the apprehension of God’s mercy in Christ to such as are penitent, he so grieves for and hates his sins, as that he turns from them all to God, purposing and endeavoring constantly to walk with him in all the ways of new obedience.

Q. 101. What is the preface to the Ten Commandments?
A. The preface to the Ten Commandments is contained in these words, I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage. Wherein God manifesteth his sovereignty, as being JEHOVAH, the eternal, immutable, and almighty God; having his being in and of himself, and giving being to all his words and works: and that he is a God in covenant, as with Israel of old, so with all his people; who, as he brought them out of their bondage in Egypt, so he delivereth us from our spiritual thraldom; and that therefore we are bound to take him for our God alone, and to keep all his commandments.

Q. 153. What doth God require of us, that we may escape his wrath and curse due to us by reason of the transgression of the law?
A. That we may escape the wrath and curse of God due to us by reason of the transgression of the law, he requireth of us repentance toward God, and faith toward our Lord Jesus Christ, and the diligent use of the outward means whereby Christ communicates to us the benefits of his mediation.

Q. 167. How is baptism to be improved by us?
A. The needful but much neglected duty of improving our baptism, is to be performed by us all our life long, especially in the time of temptation, and when we are present at the administration of it to others; by serious and thankful consideration of the nature of it, and of the ends for which Christ instituted it, the privileges and benefits conferred and sealed thereby, and our solemn vow made therein; by being humbled for our sinful defilement, our falling short of, and walking contrary to, the grace of baptism, and our engagements; by growing up to assurance of pardon of sin, and of all other blessings sealed to us in that sacrament; by drawing strength from the death and resurrection of Christ, into whom we are baptized, for the mortifying of sin, and quickening of grace; and by endeavoring to live by faith, to have our conversation in holiness and righteousness, as those that have therein given up their names to Christ; and to walk in brotherly love, as being baptized by the same Spirit into one body.

So, because the majority are uncomfortable with this, a few–who have managed to rationalize a concept of the Reformed Faith that does not really allow for those statements–have the opportunity to portray the minority who believe the above as heretics.

Those four questions and answers. That is all.

Everything else is strategy.  You can read the document linked in the sidebar, but it won’t add that much, I don’t think.