This is not what the parent is talking about. "Corps that self insure" is corporations that are so large that it's more effective for them to use a large bank account as the insurance plan for their employees than to buy a corporate policy from an actual health insurance company.

Huge companies like SAP or Microsoft or Oracle will do this, even though they may also hire a traditional branded health insurer to "manage" this large-bank-account health plan (i.e. give out cards, negotiate with hospitals, etc.). But the bank account (brokerage account, really) remains in control of the corporation, and the traditional plan premiums are not paid to the health insurance company named on the card. Fees for managing the plan are paid separately. Doctors and hospitals get paid from the corporation's account. This is what the parent means when they say that the corporation has visibility into employees' healthcare usage.