In addition to the other comments, I think what differentiates a discovery like this from manufacture is the serendipitious nature of the act of discovery. Manu

In addition to the other comments, I think what differentiates a discovery like this from manufacture is the serendipitious nature of the act of discovery. Manufacturing something implies that you have a regular process to make it on a large scale. But this was a chance discovery. The scientists shot some uranium nuclei into doughnut shaped gas cell hitting a rotating target of plutonium nuclei. This was a new method of creating and measuring heavy isotopes that they say makes the process easier, so it would be fair to say that they "invented" the process. They ended up with a bunch of ionized particles produced by the collision. They then measured those particles via time-of-flight mass spectrometry -- essentially, the velocity of the particles in the gaseous medium could be used to precisely determine their weight to an unprecedented level of accuracy. But to their surprise, among the various isotopes they measured, was one uranium isotope that nobody has ever encountered before. You could say they "made" the isotope in the particle collision process, but it wasn't a deliberate goal or by product. Hence it was a discovery. If there turned out to be an industrial use for this newly discovered isotope, and engineers came up with a way to produce it on a regular basis, then certainly at that point you could say it was being manufactured.