Thats a pretty slim article, and then they pick a very slow erupting volcano, Kilauea, for a direct comparrison. Why not Mt. St. Helens 1980 eruption, the Mt. Pinatubo eruption, or other Plinian class and above eruptions?
It is a slim article, and I wouldn't want to be the volcanologist assigned to sample an eruption like Pinatubo.
However, the basic composition of volcanic emissions doesn't change with volume. Volcanic volatiles are water, SO2, and HCl, primarily. If Pinatubo had been a significant source of CO2, the measurements of CO2 at Mauna Loa on Hawaii (where the famous Keeling curve of increasing CO2 in the atmosphere is compiled) would have shown an effect. Pinatubo didn't directly affect the atmospheric CO2 composition a whit -- however, the cooling effect that Pinatubo's eruption caused, due to SO2 in the stratosphere, actually affected the seasonal change in CO2 in the Keeling curve over the next two years.
COSPEC is used to monitor SO2 emissions to detect precursory volcanic activity. If CO2 was useful to monitor in such a fashion, they'd monitor it, too.
Ol Doinyo Lengai, the one carbonatite lave volcano on Earth, probably emits more C02 than all of the other volcanoes on Earth in an average year.
Here's another article: