As per the details in the Ref Manual; the ADC XBAR interrupt would need to be mapped to group 2 of the corresponding XBAR interrupt mapping configuration. However, for ADC ISRs, the flag is mapped to group 0 as well as group 2; as in the screen shot below.

This currently not a blocker as the ADC interrupt is getting generated through XBAR.
This issue was from the context of the below issue.
Creating the ticket for reference to get to know when the fixed MCAL would be available to be used in the project.