QColor constructor/setters taking #rrrrggggbbbb and #aaaarrrrggggbbbb discard data

QColor documentation says that it's possible to build one from such a color string. However, the parsing discards the second byte of each channel, resulting in a loss of precision:

For instance, QColor("#ff0000000000") has red == 1.0 instead of 0.996.

Given that QColor can represent 16-bit color quantities exactly, this seems like an historical quirk.