FV is not flawed because it regards the baptized roles as God’s heritage. Rather their error is found in their doctrine of regeneration, which suggests that the non-elect can, for a season, enjoy through water baptism the grace of faith and definitive sanctification prior to falling away. Consequently, FV has no place to ground the assurance of salvation that is available to the regenerate because the system allows for even a reprobate to receive the same measure of regeneration and faith as the elect. (Assurance becomes predicated upon the secret decree of perseverance, which cannot be known being a secret.) All of that stands in stark contrast to the biblical teaching – that the Holy Spirit bears witness only with the true believer’s spirit according to the unambiguous word of promise which states that all who God calls, He justifies and will glorify.
It expresses precisely what I hoped to have expressed in my previous reviews of Leithart's book, The Baptized Body.