An economist makes the following claim: 'A 3D bar chart that plots income levels for ten consecutive income groups (deciles) for every country, with countries ranked from poorest to richest, is a misleading tool for comparing the degree of internal inequality. The chart is effective at showing the massive gap between rich and poor nations, but it visually masks the significant income disparities that exist within the poorest nations.'

Evaluate the economist's claim. In your answer, first explain the specific visual feature of such a chart that supports this argument. Then, discuss a potential negative consequence of a policymaker accepting the chart's visual impression at face value without consulting other quantitative data.