You are conflating independent approaches with mixed mode.
They are different, one does not lead to the other.
No, I'm not. I'm perfectly aware that they aren't synonymous.
But the proposed R3 concept of operations of necessity implies both:
a) mixed mode on one runway for the bulk of the day (because arrival and departure demand is fairly evenly balanced, except for early mornings and late evenings) with the other two operating segregated arrivals and departures
and, therefore
b) simultaneous approaches on the mixed mode runway and the arrival one, which 50% of the time will mean two adjacent runways (hence the CAA's comments above)