I think it does, yes. As far as I can tell, MIDI events for AU plugins always reach the plugin through the AUMethodMIDIEvent callback, which accepts the status byte, data bytes, and timestamp all as individual arguments. I don’t see anywhere in that code where we might accidentally be mangling the timestamp or event types, for example.
The AU utility classes do also have a HandleMIDIPacketList function that accepts a PacketList and unpacks it in the way outlined in the thread you linked. However, this function doesn’t seem to actually be called anywhere. Even if there did happen to be a bug in the implementation of this function, I don’t think it would affect JUCE plugins because the function doesn’t seem to be used.