That 2020 Biobank study is one of about 6 other similar studies
related to the one Optimizing Nutrition used for its BMI article, posted here before, using a sample of 3.6 million adults. Optimal BMI for Longevity and Optimal Health (And How to Achieve It)https://optimisingnutrition.com/what-is-a-healthy-bmi/

Risk of 16 cancers across the full glycemic spectrum: a population-based cohort study using the UK Biobank https://pubmed.ncbi.nlm.nih.gov/32859587/

Neither of these articles has associations to diet. There are diabetics who use the high carb Mastering Diabetes, Dr. Mcdougall Starch Solution or Dr. Bernard Reversing Diabetes plans. I think lowish carb is better for controlling BG, but a Low fat high carb diet is another option to lower HbA1c.