Hi,
I'm sorry for the inconvenience.
I looked at the datasheet of the EVK-IRIS-W1 and in page 15, it states the following SDIO information "SDIO as peripheral only".
The SDIO can be used for the NCP application using another MCU or MPU as host. For instance, an i.MX RT1060 manages the application code while RW612 handles Wi-Fi, Bluetooth Low Energy, and IEEE 802.15.4 stacks. You can find more information regarding this in UM12133 and UM12095.
Regards,
Daniel.