The battery drain is in relation only to OEM third generation stereo's (RN510, RCD510 etc).
However, with aftermarket stereo's, you need to give it a switched live as it is not integrated into the quadock plug.
Preferably an aftermarket HU should have a CAN interface box - giving it a switched live, MFSW controls, dash dimming, track info on MFD etc. This is a different box to the CAN gateway and only applies to aftermarket HU's.