The "just" makes it sound like this is a minor point. This is a huge point. Enterprises are forced by their customers and regulators to show that terminated employees lose access immediately. There are two ways to make that happen: force everything to flow through a VPN, and SCIM. Most SaaS providers do not support IP allowlisting needed to enforce that all traffic flows through the VPN, and the only alternative to enforce that user sessions are terminated immediately is if the SaaS keeps sessions in a database and those sessions are revoked as part of SCIM. Otherwise the sessions could continue to be valid for days or even longer, presenting a risk of allowing terminated employees to wreck untold havok.