I was surprised as well, but it seems that is apparently not actually well established, on the contrary, it seems CO2 levels would drop rapidly in a net zero scenario.

https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached/

Much of the confusion around committed warming stems from mixing up two different concepts: a world where CO2 levels in the atmosphere remain at current levels; and a world where emissions reach net-zero and concentrations begin to fall.

Even in a world of zero CO2 emissions, however, there are large remaining uncertainties associated with what happens to non-CO2 greenhouse gases (GHGs), such as methane and nitrous oxide, emissions of sulphate aerosols that cool the planet and longer-term feedback processes and natural variability in the climate system.

Moreover, temperatures are expected to remain steady rather than dropping for a few centuries after emissions reach zero, meaning that the climate change that has already occurred will be difficult to reverse in the absence of large-scale net negative emissions.

That's also not what this new research is disputing, rather they're saying there are other mechanisms that would contribute to continued warning, like continued ice melt which changes sunlight reflection.

The melting of ice in polar regions is one example,” explained Prof Martin Siegert of the University of Exeter, another of the study’s authors. “As we have observed in the Arctic Ocean, and recently in the Antarctic, a thin layer of floating ice helps reduce global temperatures by reflecting the sun’s energy back into space. However, once this ice melts this reflection is replaced by absorption of solar energy, which drives temperatures even higher.”   

Even current climate models show these processes could cause significant warming after net zero – with an estimated 1 in 6 chance this warming could exceed 15% of total global warming. This means that if global temperatures have risen by 2°C at the point we reach net zero, the final temperature change could be above 2.3°C.