g.getFont does not return font set by g.setFont

I just wrote a little "program" to find out which fonts on a Bangle.js 2 will be reported properly and which will not:

print('which fonts will not properly be reported?');
print('');

  let FontList = g.getFonts();
  for (let i = 0, l = FontList.length; i < l; i++) {
    let Font = FontList[i];
    g.setFont(Font);
    if (g.getFont() === Font) {
      print('==  set: "' + Font + '", got "' + Font + '"');
    } else {
      print('<>  set: "' + Font + '", got "' + g.getFont() + '"');
    }
  }

Outcome:

>which fonts will not properly be reported?
>
>==  set: "4x6", got "4x6"
==  set: "6x8", got "6x8"
<>  set: "12x20", got "Custom"
<>  set: "6x15", got "Custom"
==  set: "Vector", got "Vector"
>