Unable to restrict user access to source type (Supplier, Inventory) for creating requisitions

Summary:

We have a requirement to restrict the visibility and access to the source type field in requisitions for a specific group of users. Specifically:

• Certain users should only be able to create Internal Requisitions (source type: Inventory).
• Others should only be able to create External Requisitions (source type: Supplier).
• The source type should also be hidden or restricted based on the user’s profile when entering requisition lines.

To implement this, I have already removed the privilege "Create Requisition With Inventory Destination Type" from all roles assigned to the targeted users.

However, the expected restriction was not reflected, and users are still able to access and select both source types.