I'm not sure I follow your point? Even without solar power, storage is an important part of many grids e.g. meeting peaks with pumped storage hydro.
Are you saying that solar thermal is enough storage for a predominantly solar grid? I'd suggest it isn't. I'd also suggest that solar thermal is a type of storage solution and it's time-shifting properties are one of the things that make it useful.
You're right that solar thermal is technically a type of storage system for solar. But that wasn't countenanced in the article -- wherein we're told the (availability) problem of solar can only be solved by either fossil fuel power plants or storage systems.
My point is that this is either a flawed or a disingenuous premise.
There's myriad ways we could deal with gaps in sunlight availability: nuclear fission (not a fan, but undeniably one way), biofuels (also not a fan, but ditto), reduced demand / opportunistic usage patterns (to ameliorate the effect - not easy, but disturbs me that questions about energy usage never include 'reduce' or 'adapt' in the list of considered answers), and, most importantly, a stack of renewable options that are not constrained by the vagaries of sunlight -- geothermal, wind (terrestrial and tethered), wave, tidal, and hydroelectric spring to mind.
You don't need pumped hydro. The wonderful thing about hydro is it throttles easily, and leaving water in the lake is equivalent to putting more water into the lake.
When the reservoir is full, Cruachan Power Station in Scotland can operate for 22 hours before it is emptied. Also, it is required to leave 12 hours water in the lake at all times to provide emergency cold start backup on the grid. If it wasn't pumped hydro and was only working from runoff, then it wouldn't work.
Are you saying that solar thermal is enough storage for a predominantly solar grid? I'd suggest it isn't. I'd also suggest that solar thermal is a type of storage solution and it's time-shifting properties are one of the things that make it useful.