Catholicism, A Branch of Christianity?

I heard a Catholic priest describe the Church in this way in a homily recently, and though I don’t know what he actually meant, the metaphoric reference would be more accurately used by describing the Church as the tree, and other ecclesial communities calling themselves Christian, are more aptly described as fruits that have fallen from the tree of Christianity—the Roman Catholic Church—and are now laying on the ground slowly rotting as the distance between their past, before the Protestant Reformation when they were still part of the Church, and their present, clearly showing their increasing distance from God, for the longer they are lost, the further they are from God.

The singular truth of the Church is explained most recently by the document from the Congregation of the Doctrine of the Faith in 2007, Responses to Some Questions Regarding Certain Aspects of the Doctrine of the Church.

Truth is from the Church, the Roman Catholic Church—founded by Christ—only, and whatever bits of truth exist in other ecclesial communities came originally from her, but the longer the bits of truth remain separated from her fullness of truth, the more degraded the bits become, as they lay upon the ground where they have fallen, rotting as their source of life, the tree of the Church, grows without them.

This is analogous to criminals, who, through their longevity within the criminal world and living by its truths, the greater the distance between them and God; and the more difficult to find the way back.