[NY] Why would our outside vendor website company be listed as an Administrator within Microsoft

The company I recently joined's website vendorlets call it GreatSites, although described as an outside vendor, appears to have been provisioned with an company-domain Microsoft account and treated as an internal member of the company's Viva Engage network, with administrator status in the organization's "All Company "community. Microsoft says B2B guest users cannot be added to the All Company community. Outside vendors normally can be invited to ordinary Viva Engage communities as guests, but not All Company.

Why is the admins on "All Company" the one employee at my company besides myself, a high up Board Member who doesn't even use that email (he uses gmail), and our website vendor? Is it poossible my coworker is actually receiving payment for operating our website under a different name? I don't get it?

Thanks!