It matters because it's part of our history in regards of awareness to the technology and research and development which we lacked timewise and human resources wise. People in the 60 potentially worked less on these topics in Germany than in France.
The density is relevant in point of risk.
It's easier to find empty spots in France or more very rural ones than in Germany.
Also additional to this, France is more centralized to Paris.
How does that matter today?
> Germany has double the density of France which makes nuclear even harder to do.
Yes, same is true for any other source of energy.