That is wisely stated, but Latter-Day-Saints and Jehova's Witnesses and Arians, and Bogomils and Gnostcis call on Christ and Apostoles' words, Gospels and "gospels."
His intent was to show that one could trace the faith backward through history no matter what name those believers went by
But it's not the same faith. Heresies existed alongside the Church.
I've already said that his historical search was faulty.
His thought, though, that one could trace Christianity by tracing legitimate Christian teaching, has merit.
If your defining heresy as "wrong belief" than looking at the marian doctrines it is clear it is your church and the RCC that are heretical, not various Christian churches that placed Scripture first.