it should try. because it's using gdp per capita it's stating that it cares how the entire gdp is averaged out over the entire population. the more inequality there is the less useful or representative this averaging out is
Measuring median also ignores that the upper middle can be doing very well, as it's literally just a slice from the 50th percentile.
It's like the US, where the top 10% make as much as the top 1% in Canada (as an example), but if you simply take the median it ignores the massive middle and upper middle class in the US.