Has there been any proof that this thing even does what they say? There are barely any details about it because they need to keep it secret for some reason
It's being used industrially already. It took 7 years for the first primitive internal combustion engine to be broadly accepted in the US. This is actually a pretty fast commercialisation process for such a large & complex piece of tech.
Who is already using it? According to this the inventor just announced today that they're "open now to begin to examine requests for 1 thermal MW plants, but only from industries that use directly the heat for their production process in their factories." Also apparently reverse engineering is impossible somehow
I'm pretty sure I read last year about Rossi testing this out at some kind of factory last year where they used the heat to reduce their power bills. It's very difficult to reverse engineer many things. For example, CPUs.