The format documentation 1.4.8 (and all previous versions) shows the default value of loVel to be zero (0). A MIDI Velocity of zero indicates a Note Off message, and cannot be present in a Note On message (this would turn it into a Note Off message). So why is the default the wrong value?
It should be 1 (and never zero). One (1) is the lowest value that you can have for a MIDI Velocity value in a Note On message.