This is the response I received from engineering on your crosstalk question. It does a much better job at explaining it. NOTE: crosstalk is not an issue with terminated inputs.
This specification is only meaningful as pertains to inputs which actually have sources connected to them. One never 'listens' to unused inputs.
When an adjacent input is TERMINATED with the average source impedance (as from CD players, tuners, etc.), of roughly 100 Ohms, the crosstalk falls to levels below the noise, in the area of below -120dB up to 1kHz, and below -105dB up to at least 10KHz. Thus, the crosstalk to an actual signal-producing source is below the noise, and thus inaudible.