Not strictly true... there are Typhoon production lines in both Germany (Manching) and Spain (Getafe); and they've been running for over twenty years. It was part of the "everyone gets a production line, everyone gets a development / integration / test setup" deal.
Note that the Typhoon's intellectual property was shared in full, between the four nations; I implemented one radar mode specified by the Italians, and another specified by the Spanish; and even had a German design engineer reporting to me at one point (I hear he did a good job of porting our software onto the Tranche 2 processor). It's amusing to see Dassault getting all precious about sharing its understanding and IP, but that's the price of being in a consortium.
Note also that there were seven Typhoon prototypes; DA1 through DA7. Each had a focus on a different area of test; e.g. DA5 did most of the radar trials. There were also five "Instrumented Production Aircraft" used for weapon trials, etc.
Suggesting "we only need one prototype", suggests a lack of any background in aircraft development...
I have not suggested one prototype. I have said "leave it to those who have produced successfuly 6 generations of widely exported and combat proven aurcrafts".
Neither Spain nor Germany has any claims to lead such a project. The jet aircraft with the most combat kills to its name is French, not German, US or Spanish.