Does Project Billing Specialist Role need to be customized to enforce invoice workflow approval?

Summary:

Content (please ensure you mask any confidential information):

We have the Project Contract Invoice Approval Workflow enabled to route approvals to Contract Administrators, however the Billing specialist users are still able to approve using the Approve button on the invoice screen. Does the role need to be customized to remove the button, regardless of the workflow being enabled?

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):