The article is too US-centric to a fault. Basically all project's costs after 1970s balloon to an extent. Japan's cost has risen. French, while only slightly, has risen. Same for India. Only S. Korea have seen construction prices fall, but notice the price bottoming out after the 1990s. It's only maintaining the price, not getting lower.

Regardless, these other countries didn't contribute that much to increase global nuclear power capacity. In both India and China nuclear doesn't even count as the majority in their low-carbon energy mix, which is still dwarfed by the massive deployment of coal. S. Korea is slacking on low-carbon sources in general. Japan has lost trust (rightfully) on nuclear and decided to reset their entire nuclear generation capacity. No country has expanded their energy grid with nuclear. Except France, who only did it because of the oil crisis.