Did you read carefully what you had written in the main text when you compiled the headline? Did you make a typo and forget to include the word plant based . The reduction in risk is a comparison between Low carb higher in plants and those higher in animal fats and proteins rather than any overall reduction in risk.
Indeed in the body of the report you say
"The researchers analysed data from 4,502 women, all of whom had a history of gestational diabetes. Over 20 years - from 1991 to 2011 - the participants answered food-related questionnaires, and the researchers calculated each participant's adherence to low-carb dietary patterns. 722 participants developed type 2 diabetes during the study, with the risk much lower for women who followed a low-carbohydrate diet. "In the prospective cohort study with up to 20 years of follow-up, we observed that a dietary score representing a low-carbohydrate, high animal protein and high animal fat dietary pattern was significantly associated with [type 2 diabetes] risk among women with a history of [gestational diabetes]," and you quote one of the researchers as saying
"Women with a history of [gestational diabetes] who follow a low-carbohydrate dietary pattern may consider consuming plant sources rather than animal sources of protein and fat to minimise their future risk for [type 2 diabetes]."
Actual conclusion from paper
"Among women with a history of GDM, a low-carbohydrate dietary pattern, particularly with high protein and fat intake mainly from animal-source foods, is associated with higher T2DM risk, whereas a low-carbohydrate dietary pattern with high protein and fat intake from plant-source foods is not significantly associated with risk of T2DM." (nothing about reduced risk compared with normal either which is not surprising given the hazard ratio of being 1.19 (95% CI, 0.91-1.55)