That is a subtle one… I agree, its a bug.
Try this for a workaround. Change the code of “Faulty” to:
header = ["1", "2", "3", "4"]
data = []
data.append(["One",1,1.000001,1.000001]) # sets the types
newDataSet = fpmi.dataset.toDataSet(header, data)
newDataSet = fpmi.dataset.removeRow(newDataSet,0)
fpmi.tag.writeToTag("[Client]testData",newDataSet)
fpmi.nav.openWindow("Window 2")