TIDM-02002: Usage of ISO7820FDWR

Part Number: TIDM-02002
Other Parts Discussed in Thread: PMP21561, PMP21999

Hello 

I have a question regarding the TIDM-02002 reference design.

There is an IC used in the interface from PWM signals for the secondary side SiC drivers, with part number ISO7820FDWR. 
I wonder why this isolation stage is used, while the SiC drivers already isolate the signals using UCC21530QDWKRQ1 in the PMP21561 Safety Isolated Secondary SiC MOSFET Driver reference design.
Is this stage mandatory?

Thanks In advance