Based on an internet seach (type: "National Reich Chuch" cross into google), it appears to be true, as I found a number of sites supporting it and none refuting it.
What the sites say is that there was a 30 point program for the chuch and point 30 was:
30. On the day of its foundation, the Christian Cross must be removed from all churches, cathedrals and chapels...and it must be superseded by the only unconquerable symbol, the swastika.
One of them references a book: The Rise and Fall of the Third Reich, William L. Shirer, P. 240
