The Audio Codecs Evaluation kits were designed to showcase the part with the USB Audio as a source, not as a recording input.
The Audio codec EVkits include a TOSLINK SPDIF transceiver, which showcase the input and output capabilities of the IC with a compatible TOSLINK SPDIF device such as the AP2700.
An alternative way to monitor record path via the Digital audio interface is to program the codec to follow the signal path mic source -> ADC -> i2S-> DAC -> Analog out.
Another option to test the record path digital output (mic source -> ADC -> i2S) will be to implement a compatible device that can interpret the i2S signal out of the codec. This is done with a device like the AP2700 and the PSIA-2722 Programmable Serial Interface Adapter.
You can also use a microcontoller that has an I2S engine to decode the signal.