Since ac108 and wm8960 are both I2S audio chips, I would guess that they exist to support current HAT’s that have those chips.
EDIT: A quick check of the two source code files dts (device tree source), before they were compiled with a dtc (device tree compiler) to generate the dtb’s would match that assumption:
jh7110-visionfive-v2-wm8960.dts
jh7110-visionfive-v2-ac108.dts
They both have an I2C interface for control and one or more I2S interfaces for audio samples.
Looking through the board schematic, there are no microphones or direct audio input. So if you wanted to add audio input, (or higher quality audio output) then you could do that by adding a HAT (or a USB sound card or MIPI-CSI or …).