I don't really think these studies show that acute blood sugar level elevation is causing the damage you are talking about. The first one talks about how TII diabetics tend to have lower β-cell count and higher apoptosis frequency, but that doesn't mean they go through waves of apoptosis more frequently (ie: during blood sugar spikes), it means that they have a lower life span. The study doesn't establish causality, so it's unclear whether diabetics have lower β-cell count because they are diabetic, or whether lower β-cell causes diabetes. It is a great study though, pretty well designed and building on kind of amazing resources from the Mayo Clinic.
The second study is interesting but extremely limited due to the fact that it was does in vitro. The problem is that it's talking about kidney fibrosis, or scarring of the kidney due to inability to regenerate. But when you remove much of the kidney and the surrounding body and then attack the kidney with glucose of course there is damage. That doesn't mean that in vivo the body can't deal with it. Kidneys do have a hard time regenerating, so it's an interesting foundational study, but I'd hardly call it "a lot of accumulating evidence."