Actually, what it looks like is even simpler. The extension cable
contains a four-port hub chip (which is the most common commodity chip)
and haven't bothered changing the descriptor to tell the computer only
one port is actually active. So only one port can be activated, and the
others are stubbed out in some evil way. In that case, it should be
noisy but harmless.
I will do some more testing then.
Is there a way to get rid of the messages?