It seems like that the label fontSize is 10 instead of 11 and the font weight is regular instead of FontWeight.w500

The font weight of the CupertinoTabBar is not set and defaults to regular. However, in the sketch file from https://developer.apple.com/design/resources/ the tab bar label has a font weight how 500 / medium.