[nl]

Their terminology is defined here: https://www.nrel.gov/docs/fy19osti/74426.pdf

I think it is mostly use correctly. They genuinely are talking about "the total possible instantaneous discharge capability" when they talk about "storage capacity increasing".

I think this is because in table 1 of the linked doc they list where batteries help the energy market and most are capacity (as in power delivery capacity) limited, not stored energy limited (ie most of the uses are measured in "hours" of stored energy or less. In general it reads as the limiting factor is power capacity, not energy storage capacity).

I do think the graph in the linked article (https://www.eia.gov/todayinenergy/detail.php?id=54939) should use terminology consistent with https://www.nrel.gov/docs/fy19osti/74426.pdf though.