I think he's referring Rabisu and Malus, though that only accurately describes Rabisu. Malus was still alive when declared. Not sure if we view Malus as dead or in a very deep meditation (char/family deleted anyway).
If that's the case, I believe it is pretty much doctrine, though not one anyone loses any sleep over. ESA is very much a religion that focuses on the present, rather than getting worked up over the past. So people are more interested in listening to the current prophet speak, than arguing over whether past nobles were prophets.
