How do I use supplier contacts in MFS if I can't link them to a user?

In response to this question: I was told that MFS MP only supports Employees, not supplier contacts.

Are there restrictions for a third party resource to access functionality in Mobile Field Service?

Yet, this document indicates that I should be able to add supplier contacts:

MFS Multi-platform Apps Only Works With Employees, Not Supplier Contacts (Doc ID 1619377.1)

I am unable to link the resource in CRM to a User Name in Oracle if the Resource is a supplier contact.

I have verified that the Patch 17938842:R12.ASG.B has been applied, but I am still unable to link a supplier contact to a user, which is what is done to get an employee to have a username and password to access the MFS-MP app.