A percentage chart does not always have to start at zero. Scaling the y-axis to the range of the data is commonly used to make within-chart trends easier to see. I don't think this is evidence of a nefarious motive... it looks more like a stylistic choice.
It doesn't have to, but shifting the y-axis to exaggerate differences is like the most textbook example of deception in statistics. In that sense, if you want your work to be taken seriously, especially when it purports to be more accurate than other statistics, it's certainly a choice.
