Nice to see an interest in the science behind the fish we love to keep.  

Off hand, I don't know the answer. I'm also not sure that grouping C. moorii with Placidochromis makes sense. What Placidochromis species have the nuchal hump that rivals what moorii have?
I tried to look up the characteristics that define Cyrtocara. The best I could get is the source that first described it:
Boulenger, G. A.   1902 (1 July) [ref. 567]
Diagnoses of new cichlid fishes discovered by Mr. J. E. S. Moore in Lake Nyassa. Annals and Magazine of Natural History (Series 7) v. 10 (no. 55) (art. 11): 69-71. [Date of publication from Evenhuis 2003:36 [ref. 27365].]If someone has access to a good library catalog, they might be able to find a digital copy.
I also found some allusions to Cyrtocara being used to describe species previously referred to as Hapolochromis originating from Lake Nyassa (better known now as Lake Malawi), distinguishing them from various Hapolochromis from other lakes. There was also some suggestion that C. moorii are perhaps most closely related to some deeper water, less studied species (and I forget the genus I found that those fish reside in currently). 
As for what makes a fish belong to Placidochromis, I couldn't find a good paragraph on that either yet. I was amazed to see that there are 43 described species belonging to Placidochromis currently! I knew that there were a few, and a few more species found/added since the new century began, but there's 4-5 times the amount I thought there were.  
