> Among youth with type 2 diabetes ... Sociodemographics and, additionally, mean body mass index, fasting and random glucose, and HbA1c levels were not different from 2016 to 2021.

They're talking about these values in the diabetic population, not youth in general. They are simply saying there are more diabetics, but they have similar characteristics as pre-pandemic diabetics. This is expected.

The study shows incidences on the scale of 15-25 cases per 100,000. The relative incidence ratio may have increased significantly but the absolute increase was small enough that the handful of people with higher A1C wouldn't have budged the average.