Of the 11 dietary factors considered, three had an outsized contribution to the rising global incidence of type 2 diabetes:

Insufficient intake of whole grains,

No, 'lack of whole grains' does not cause diabetes, though it is less likely to cause diabetes than refined carbohydrates

excesses of refined rice and wheat,

Yes, and also obviously sugar

and the overconsumption of processed meat.

I... don't think so. Processed meats contain nitrites which are credibly linked with colon cancer, but I have never heard of this association with type-2 diabetes. Doing a search of the literature, I can find only a single study from this year, which has never been cited by anyone, which appears to be what this article is referring to

https://pubmed.ncbi.nlm.nih.gov/36649248/

While I could not another study to support this, what I did find was a study saying nitrites DECREASED the risk for type-2 diabetes that has been cited by 81 other studies

https://www.sciencedirect.com/science/article/abs/pii/S1089860317301131

and a few more

Potential Therapeutic Effects of Nitrate/Nitrite and Type 2 Diabetes Mellitus

https://brieflands.com/articles/ijem-71999.pdf

Dietary nitrite supplementation improves insulin resistance in type 2 diabetic KKAy mice

https://www.sciencedirect.com/science/article/abs/pii/S1089860314004996

I am gonna say this link with nitrites and type-2 diabetes sounds very fucking dubious, it seems better supported as a treatment for type-2 diabetes than a cause. Though yes, diet is obviously the cause of type-2 diabetes, I would not take this advice seriously.