SAP IAS - Do we need users in SAP IAS if we use corporate IDP for Authentication

[S0015423014]

Hi Team, 

If we have corporate IDP and IAS is used as proxy IDP, do we need to sync the users from any source systems to SAP IAS?  I know for the fact that for SF story reporting the users must exist in SAP IAS. But apart from that only for authentication to any other application, do we need users in SAP IAS when we use corporate IDP ?

Here is a use case: 

I want all the users to get authenticated against the corporate IDP (e.g. Azure), when they are accessing any of the below applications. So in that case do we need the corporate users to exist in IAS? 

1. S4 HANA Public Cloud

2. SAP SAC

3.SAP ARIBA

Thanks

Sanjay