The less favourable the existing geography, the harder it will be for a state to "just" build a pumped storage facility like Dinorwig. Dinorwig is basically ideal, the mountain was already right there, with a nice lake at the bottom and a quarry that had closed or was about to close that could be re-used as the top lake. It's far enough away to reduce the amount of random BANANAs‡ who get involved yet not so far as to make the infrastructure cost prohibitive (for HV power lines to the facility). The UK hasn't built lots more because it doesn't have dozens of other mountains with lakes next to them just kicking about for the work, and any it does have are deemed environmentally important (e.g. something rare lives in the lake or on the mountain).

China has two advantages: One it's fucking enormous, there are bound to be places with mountain lakes that weren't needed for anything else more important. Two under an authoritarian government there's no prospect of protest against the plan even if it's catastrophic for some groups.

‡ NIMBYs but more so, Build Absolutely Nothing Anywhere Near Anyone.