Yeah, but what about their statement “...reaping far more energy from the reaction than you put in.”
Doesn’t that seam impossible?
One of the places where these schemes all fall apart is that somehow or other you have to confine the fuel at high density as the nuclear processes proceed. That has proven to be impossible, but even if not, the confinement process requires a lot of energy, exceeding that produced by the fusion process itself, as it turns out.
Why should it?? Any fueled engine "reaps far more energy...than you put in". See your car. You input a tiny amount of energy from your car's battery to get things going, and then "reap" hundreds of miles of travel energy from the fuel. This is no different. It is all about getting (and keeping) things going.