If a CC settlement agreement does not include anything about reporting it to the credit bureaus what can happen and do they have to report it anyway?

There is no law that compels any creditor to report to the credit bureaus. It is voluntary.

If the account is already being reported to the bureaus as a derogatory, with a balance, it would be in your best interests to have the settlement shown. But other than requesting this, or attempting to update your credit yourself, there is no way to compel this.