The supplier records are supposed to be a central repository however it only allows supplier contacts to be Supplier Users. There should be a separate place within the central supplier records to add supplier contacts for information only that do not need to be Supplier Users (and don't need to receive any auto-generated emails, logins, etc). For example, a supplier account manager may be a Supplier User but a member of the Delivery team, Customer Success team, Project Manager (where we may need easy access to their contact information - job title, email, tel) will unlikely need to be a Supplier User.