Your organization is on the Slack Enterprise Grid plan.

Slack’s Enterprise Grid documentation clearly states:

"Syncing IdP groups with Slack allows you to automatically manage workspace membership, channel membership, and access control based on IdP group assignments."

Key benefits include:

Automatically provisioning and deprovisioning members to specific workspaces (A).

Maintaining mandatory membership in designated channels (B).

Maintaining mandatory membership in designated workspaces (C).

Assigning system roles, approved apps, or admin roles (D, E, F) is not automatically handled through IdP group syncing.

(Reference: Slack Administration Study Guide - Identity and Access Management)