This seems like sensationalist science journalism. It says "scientists" aren't happy about the decision, but the only evidence it provides is this singular quote:
>But some are unhappy with the decision, and worry that planetary studies are being truncated too soon. “Scientifically, I just don’t feel that we’re at diminishing returns yet,” says Kelsi Singer, the mission’s project scientist at the Southwest Research Institute in Boulder, Colorado.
Like, ok? The whole reason they're shifting to heliophysics is because there are no other objects they're aware of for this probe to explore. What else is it going to do? What do these "scientists" want it to do instead?
"There’s going to be a boarding party on the first of October next year,” says Alan Stern, the mission’s principal investigator"
I think the unstated is that the original group of scientists feels like they are being put out to pasture in favor of a new set of researchers. But as you mentioned, if there aren't any more Kuiper belt objects on the "horizon", it seems like the right move.
Maybe I’m wrong, but having it classified as a planetary mission probably funds their positions and a lot of continued research (even if the research is based on data already taken). Reclassifying the mission probably means the scientists need to look for new sources of funding. So I get that they’re not happy, but it sounds like a rational decision on NASA’s part.
Plus the door is still open if another belt object is found before the spacecraft leaves the area. Anyway it's not like they can put the brakes on and stay: how much delta V can they have fuel left for ?
>But some are unhappy with the decision, and worry that planetary studies are being truncated too soon. “Scientifically, I just don’t feel that we’re at diminishing returns yet,” says Kelsi Singer, the mission’s project scientist at the Southwest Research Institute in Boulder, Colorado.
Like, ok? The whole reason they're shifting to heliophysics is because there are no other objects they're aware of for this probe to explore. What else is it going to do? What do these "scientists" want it to do instead?