Claims they don’t know how it works, yet, were real specific about how they built it. There is no way on God’s green Earth they built something so technically specific without knowing how it works. They simply did not say, “Hey, Vern, let’s put this here and that there together and see what happenes.”
They don't have a complete underlying scientific theory for the LENR reaction involved. That's completely different from the technical specifications involved in building the working product. The fact that the demonstrations have all been done with out any hitches ("sorry for the delay folks... just give us another few minutes (head ducking back under equipment)...") strongly suggests to me that they have a good knowledge of the critical functional parameters.
We don't have a meaningful theory for what gravity "is" either, but that doesn't mean we can't reliably make use of it in our product designs. As an engineer, I could really care less if the academics can't figure out how it works.
When I was a freshmen aerospace engineering student I recall my prof declaring that, scientifically, bumblebees can't fly. His point was that having tidy working scientific hypotheses is secondary to engineering reality. So this point on the 'con' list means very, very little to me.