Not sure about the choice of pie chart as the default leaf format (humans are bad at guessing proportions from pie charts) but otherwise it does look great and convey the information efficiently.
howdy! We use a pie chart for classifier leaves, despite their bad reputation. For the purpose of indicating purity, the viewer only needs an indication of whether there is a single strong majority category. The viewer does not need to see the exact relationship between elements of the pie chart, which is one key area where pie charts fail.