That is far from being unique. As far as I know, many powerplants use external power. For example, Fukushima depended on external power for safety - and when that power was gone, along with the backup, the reactors melted down even though they produced plenty of power at that time.
I have no idea how valid or scientific that test was, but from what I saw in photos the devices are pretty much made in a basement, by hand. I'm not surprised that some of them didn't work well. Rossi doesn't own a factory yet to make them.
Now that he apparently sold the thing, we should expect two independent developments. First, the customer may eventually tell the world what kind of a pig in a poke they bought. Unrelated to that, we should expect Mr. Rossi to learn from this experience and produce the next set of equipment for someone else. At this point he doesn't need to convince scientists and journalists anymore; his products should be doing that, at full steam.
They were just like the diesel generators that are on the building I work in. We have a battery-based UPS that has 10 minutes of capacity for the building (large computer rooms) and diesel gensets that can be online in 15-30 seconds.