Crosen:

I am about to do something that I do not think I have ever done on any forum
(and I know at some point I will regret this).
"WTF".
You are worrying about stuff that even product designers do not need to worry about and making assumptions based on a misreading of the data.

At this point I have to think that you are spending way too much time on AVS listening to the "Digital is Digital" crowd (after all a cheap cable is just as good as an expensive one), you are really putting more into this than there is.
Also after all of the reading and research that you have done on this I find it hard to believe that you still think receivers should be zero loss.

Lets start with what a digital signal (1 & 0) really is.
Digital Data is just a voltage on/off relay that works really fast a "1" is voltage on and the "0" is voltage off.

Think of 4 light switches on the wall direct connected to a bulbs (Red, Green, Blue & Clock) that must see between 4.7 & 5 volts with 50 mA each to work (this voltage/amperage is augmented by the vast majority of inline HDMI devices) .

Remember that there is 1dB of signal loss per meter of cable (assuming a good cable) plus 1dB of loss per contact point (this does not take into account added issues so as timing, impedance and trace EQ) & 1dB of loss thru circuit board.

Most sources (not including CATV STB's which have less) start with about 22 dB on signal.

Option #1: Switches direct to bulbs at 6 meters with no connection points.
Only 5dB of signal loss as there are no added points of contact.

Option #2. Switches thru AVR (1 meter cable) to bulbs (still 6 meters).
Loss here is 9dB.

At this point we have lost just under 50% of starting signal headroom (which may have been poor to start with).

There is no such thing as a zero loss device (think about your Fax machine or photo copier).

Now to the above loss lets add timing problems as this is what causes many of the real world problems.

All four of the above listed switches must keep the signal switching in a very small time window, this time window is established between source/display by the clock feed.
Here is where the real problems start.
Pull a dollar out of your pocket and look at it in side profile, the thickness of that thin slip of paper is the max allowed variance between the four feeds in the High Speed signal path (the whole signal path including source, cables, AVR and display).
If any one of the feeds has a different overall length it will affect how the signal is reintegrated at the display (what this means is that when you look at an "EYE" pattern you must look at ALL four over layed, as just one does not tell the story).

AS this is just the High Speed side we must now add to it the low speed data (to which all of the above applies).

Actually that fact that this works at all is really amazing.