The MAX98091 does not have an SPI interface. It is I2C only. The MAX98091EVKIT datasheet references SPI for the MAXQ2000 which communicates via SPI for other devices on the EVKIT board that use it, like the S/PDIF interface IC. This is transparent to the user of the EVKIT and is all managed by the EVKIT software. All communication between the MAXQ2000 and the MAX98091 on the EVKit is via I2C.