I think the interesting thing here, as the article mentions, is that correlation doesn't equal causation. There is definitely an advantage to exercise, and the brisker the walk the better, as it's good for cardiovascular fitness, joint health etc as well as burning calories. And people who are generally fitter are less likely to develop T2DM. But also people who are generally fitter/healthier are are less likely to have T2DM, and are probably also better able to move more and faster.
A potentially interesting follow-up might be to examine the correlation between number of daily steps, and pace, in patients with known Type 2 Diabetes and the reversal of the condition.