It's not really an asterisk if it's right in the title and the name of the company, is it?

They’re using the stored heat energy as heat, not converting it back to electricity.

And if it’s very cheap, does it matter if the conversion is wasteful?

I'm not saying it's bad, but it's clearly not a replacement for batteries, given its applicability is quite limited.

The question is about conversion is, is it still cheap if you add a powerplant (i.e. converting heat into electricity) and have to maintain it (moving parts, in contrast to batteries).

As I understand it, this is meant as a supplement to batteries, so that batteries can do most of the intraday load shifting while thermal can store energy over longer durations.

It's explicitly not a replacement for batteries. Did you not read the article?

It's a crucial complement for batteries. Batteries suck for seasonal storage.