That may be true to a certain aspect for the high schooler in the parent garage. Now lets look at the audio system in the 7 series.
First you have an ASK unit that supplies four amplified output channels and two digital output channels (fiber network) to a L7 amp that is coded for DSP (Digital Sound Processing). Also lets not forget also that the ASK unit has a muting system built in for the phone,( which when receives signal output is directed to the front two speakers) speech service ( the same signal transfer). The only one that signal transfer different is the PDC which gets directed to there respective corners via input.
L7 amp get 2 fiber signal that powers 1 summed center, a left rear door, a right rear door and two subs.
So in order for digital playback you have to have digital feed, for example fade your speaker to one corner and if you hear every tonal range then it is not digital its analog!!!!
ALso the clean sweep convert the signal flat also which you are correct is considered full range. That is how music is recorded in full range (Flat 0' band width) so that all the tweaking can be done on the playback, also the clean sweep corrects line level which gives both channels the same volume and voltage output.
My opinion is for the cost of the audio system in the 7's its still lacking, due to the amount of issues and the resolution BMW did was to switch manufactures due to the concept.
But I can replace the amplifiers in the car and have a cleaner more defined sound than with the L7.