They are still watching it. https://phys.org/news/2023-09-dart-impact.html gives much better details on this situation including:

The DART science team is continuing to analyze their data, as well as new information on the composition of the asteroid moonlet and the characteristics of the ejecta to learn just how much DART's initial hit moved the asteroid, and how much came from the recoil.

But now another group of researchers, led by Taylor Gudebski and Elisabeth Heldridge, used the 0.7m telescope at the Thacher Observatory located on the campus of The Thacher School in Ventura County, California to make their observations.

They quite likely already know of this and just have not reported any findings yet, likely as they want to collect more data first and have another launch planned to study this further:

Additionally, another spacecraft will launch in 2024 to study Dimorphos even closer. ESA's Hera mission should arrive at Didymos and Dimorphos in December 2026. Hera will undertake a detailed study of Dimorphos to understand more deeply how the impact affected it.

Just so happens these students published their work first. That does not mean the team behind DART are not monitoring it any more and have nothing further to report or have moved on to other work. Even if that is what the OP article seems be be hinting at.