Well, I don't know the details, if it works directly with steam then the circuits must withstand a high pressure as well no? (which can justify the higher cost)

But I thought that for thermal solar the most common case would be a molten salt circuit (high temperature low pressure) transferring heat to a steam circuit for better efficiency (and the heat storage capability of the salt)

Ah yes, the technology is not that new (it's heating with the sun after all)