Call god points are cumulative - you need 40, but they don't have to come in the same turn.
So, I imagine that if getting 40 call god points while the pretender's alive actually did something then someone would have posted on it by now, thus I assume that it does nothing.
One possibility that might have slipped by is if it gives your pretender a sort of one-time immortality. Your pretender dies, but your mad prophets have already re-summoned them.