It is perhaps sometimes true that it is "less safe than previously assumed", but I'd guess that more often it's "we figured out a way to do it _even safer_", but in either one of these cases, 40+ year old nuclear tech was and is safer than coal power plants, which is the alternative. We crossed "safer than the alternatives" and "safe enough" decades ago. The safety regime in the US around nuclear is out of control and has no connection with any outside context.