There seems to be some discrepancy between how these important cities are displayed on the map. While London and Edinburgh are displayed even at a far zoom level, Belfast and Cardiff are not. Non-capital cities like Glasgow, Manchester and Liverpool are instead shown. Is this based on city population data?

When you zoom into a level where the city names are displayed, they are still displayed much smaller than other cities.

I assume this information is based on population data, as population-wise these cities are quite small in comparison to other cities within the UK. But surely more than population data should account for whether a city is shown prominently on the map? Being a capital city of their region should also account? Their political status? I feel like Cardiff and Belfast should be shown as prominently as Edinburgh as capital cities of countries within the United Kingdom. London as capital city of the United Kingdom as a whole has the extra dot within it's circle below it's name.