That is true for the 1970's and 1980's boom of production in France, but is not true at present: the EPR they are building at Flamenville 3 and Hinkley Point C1

That is true for the 1970's and 1980's boom of production in France, but is not true at present: the EPR they are building at Flamenville 3 and Hinkley Point C1+C2 are the sum total of those reactors currently under construction, and none are currently operational, so those three are likely to be the total number ever built. It is true that the 34 CPY reactors, and the 20 P4 reactors, were produced in large enough numbers to create a skilled class of workers and engineers who were deeply experienced with building these reactors, but right now all of those workers are retired. And honestly, from observation, it appears that rebuilding competence like this is a lot harder than building it in the first place: when you are building the first time everyone- the general public, the regulators, the workers themselves- are more forgiving. When you've lost that capacity and are trying to rebuild it you have expectations set for a mature industry, but the skills aren't there to deliver it.