Can FirstName be optional in the REST API Create one contact?

Summary:

We would like to have the Supplier Contact First Name be optional. We performed a Sandbox Personalization and made the First Name optional on the UI:

We are able to manually Create a Supplier Contact in the UI without entering a value for First Name. However, when we use the REST APIs Create one contact and Create one contact address and do not have a value for FirstName, we get the Error: You must provide a value for the FirstName attribute.

Is it possible to have the FirstName be optional using these REST APIs?

Content (please ensure you mask any confidential information):