Okay, firstly I am aware that Battlescribe is.. bad. So bad in fact I'm going to write up my own personal app that does a similar thing, but ignoring that here's the query:
Raven Guard Decapitation Strike RoW
<> Limitations <>
... may only take a single Consul as part of their HQ choice.
<> Special Rules (All) <>
So, correct me if I'm wrong but my initial of the Consul rule on the following page reading is that every Centurion has the option of being a Consul, but that not every Centurion is a Consul. Which means you can take a Moritat and a normal Centurion in the Rite above, for example.