iMac G5 FireWire Ports Remain "Hot" Even When iMac is Off

From Dana Baggett,

I have discovered that the FW ports on the iMac G5 are hot, i.e., they don't shut off when the computer shuts down. This is confirmed by the iMac G5 Developer Note, pg. 30:

Important
The FireWire PHY on the iMac G5 does not operate from external bus
power. As long as the computer is plugged into an active AC power
outlet, the FireWire PHY is active and the FireWire bus remains
connected. If AC power is interrupted, the PHY will stop operating
and data on the bus cannot be repeated.