QTextLine::height is not equal to QFontMetricsF::lineSpacing

The documentation of QTextLine::height states that it should be equal to the sum of ascent, descent and leading, but in fact the result seems to be ceiled and is not the sum of the aforementioned (see: https://github.com/qt/qtbase/blob/dev/src/gui/text/qtextlayout.cpp#L1469). 

When using QFontMetricsF on the other hand `lineSpacing` does report the not ceiled height.

Either the implementation is wrong or the documentation is. In my opinion this is a bug, because as a client I cannot rely on QFontMetricsF without knowing how QQuickText is laying out its text (is it using the lineSpacing from font metrics or from QTextLine?).