I believe he is making a distinction between Christianity and Christendom. Through Constantine’s conversion, Christinity began to assume a political and territorial aspect, ie “Christendom”.
Yes, of course he is making that distinction. Christendom in this sense reflects the political/religious understanding of the Middle Ages that has been carried forward into our times in the thinking of many churchmen (who will remained unnamed) in nearly all denominations (who will remain equally undesignated). This is, to be sure, what we see shrinking all around us as the tide of paganism rises. But Christendom in this sense is a false construct, useful for historians, sociologists, geopolitical analysts, etc., but not at all to be seen as identical to Christendom (Christianity) in the full sense of the term. After all, did not Jesus say, “My kingdom is not of this world”?
Christianity was living and growing before the time of Constantine - however terrible the persecutions were - and it will be living and growing till the end of time, no matter what happens to the religio-political construct “Christendom.”