It seems the suggested termination of ADV7511 HEAC pins with 50R resistors to 1V8 fulfills the 100R differential termination requirement, but it does not terminate with correct common mode and single mode impedances. However the impedances happen to fall within tolerance.
There is one eval board schematic that has a 5R resistor to ground, that will match the impedances.
But why in one place the resistors terminate to 1V8 supply with incorrect impedances, and in one place they terminate to ground with correct impedances? What is the correct impedance network, and where does it connect to, 1V8 or GND?