The doctrine of God's voluntary condescension goes hand in hand with the distinction that developed in Reformed theology between "covenanted" merit and "strict or "proper" merit. Covenant merit is assigned to Adam in the covenant of works, whereas strict merit is assigned to Christ in the covenant of grace. ... This designation of covenant merit reflects the ontological considerations which pertain to Adam's status. It seeks to take into account the Creator-creature distinction and God's act of condescension to enter into covenant with Adam. (Andrew M. Elam et al., Merit and Moses: A Critique of the Klinean Doctrine of Republication, 52-3)
In their book, the three OPC ministers acknowledge the idea of covenant merit in the Reformed tradition especially when applied to Adam in the Covenant of Works. They then proceed to argue that the Klinean idea of merit is a novel, third kind of merit. Without going into Kline's idea of merit yet, what is concerning to me is how they do not seem to understand that they have no reason for holding on to the concept of covenant merit at all.
The three authors here defined merit ontologically. But if merit is only about ontology, then upon what basis can we talk about covenant merit? Upon what basis can Adam merit before God, that a creature can merit from the Creator? They state that it is assigned through God's act of condenscension. That is true in the sense that anything from God to Adam is condescension, but the question is not whether it is condescension but whether it is merit. Ontologically, despite Adam being sinless he is still a creature, so even before the Fall, Adam cannot merit anything from God, if one defines "merit" only ontologically.
If merit is always defined ontologically, then even Adam cannot merit anything from God, not even if one defines it a "covenant" merit distinct from strict merit. That is the argument of those like the PRCA who attack any whiff of merit, and it is valid if one defines merit ontologically. One should not speak of merit even with the idea of condescension, for how can one claim that God owes him anything just because God has condescended to Man?
The focus on ontology therefore cannot be squared with the Reformed tradition's usage of the term "covenant merit." Either one focus on ontology and discard even the notion of covenant merit, or one stop this inordinate focus on ontology.