You keep posting this link. I do not think you know what this link means. Again, nowhere in this link does it talk about DCVax, or even NWBO/Advent. I showed you a quote directly from NWBO saying what the certification covered.
The DCVax process is covered, which is why they selected this criterion. That doesn't mean it is specific to DCVax. There are plenty of other plants certified to these same standards that have no intention of producing DCVax.
I can get my license to drive a car. With it, I can drive a Ferrari. I can also drive a Ford Focus. The important thing is, I have my license. It isn't restricted to only one car.
It looks to me like each specific product needs to go through its own process of certification. At least that seems to be the case to me by looking at these stringent procedures of MHRA for certification.