I guess that with "throughout the country" you mean the US? There, building gigantic new pumped storage systems might work, e.g. somewhere on a mesa in a desert with few people living nearby (OTOH you need some source of water for pumped storage too, so a desert location is not really ideal), but in more populated locations (i.e. Europe) such a project would face opposition and interminable delays caused by all the NIMBYs living next to it.

Besides that: pumped storage is good for regulating short-term fluctuations (between day and night), not so sure about storing surplus renewable energy produced in summer to use it during winter, as the article proposes?

Location, location, location - there are many sites globally suitable for geological bulk hydrogen storage; the UK has had the Tesside site operational until recently since the early 1970s.

They were built 50 years ago. (Slightly before today).

Pumped hydrogen at Walpole is a great functional little project that eases the grid edge brown out problem. ( https://news.ycombinator.com/item?id=45332157 )

Scaling that up to the energy storage potential of the right geological structures of the sizes needed to power cities and run heavy industrial isn't as economically clearcut as you may assume.