Building aircraft is not what keeps the design teams current. You can only do that by "designing" things. So the issue is what things are Boeing military aircraft or the "Phantom Works" designing? For the Phantom Works we may not know as much of their activities are "proprietary". I will grant you that the production side is what funds a lot of the design activity.
For the F-22 Boeing built the wings and aft fuselage, including the structures necessary for engine and nozzle installation, and was responsible for avionics integration, 70 percent of mission software, the training system, the life support and fire protection systems, and the pilot and maintenance training systems.