If you think it through, this statement makes complete sense.
Some emergencies, once handled, are not that challenging to fly. An engine out scenario is relatively simple once the aircraft is trimmed out - especially if the aircraft is approved to fly on autopilot.
The QRH procedure that follows the emergency, however, may be so complex and task saturating that having the Captain complete it would remove any sense of situational awareness, therefore degrading the command ability of said Captain.
In most cases I agree that the First Officer should fly the aircraft while the Captain runs the checklist, calls company and ATC, talks to the passengers, etc. That removes any possibility that the message is diluted or changed when sent through the First Officer.
However, if the QRH is so complex (as it was in this case) that the Captain would be heads down for a long period of time, then it is better that the Captain flies and the First Officer complete the checklist. That way the Captain can monitor the First Officer while making command decisions necessary for aircraft safety.