[broahmed]

In my experience, it's not the scientists (NASA or JET in this case) that utter such statements but journalists. NASA scientists will say something like "we've encountered something new, but we're not jumping to conclusions until we've investigated fully" and then you'll see some bloggers/journalists putting out clickbait titles like "Possible alien life discovered on Mars!"

In this case, the celebration seems well-reasoned. From the article:

"It's a landmark because they demonstrated stability of the plasma over five seconds. That doesn't sound very long, but on a nuclear timescale, it's a very, very long time indeed. And it's very easy then to go from five seconds to five minutes, or five hours, or even longer."