Are you using a AGOL hosted service or a ArcGIS Server service? If it is a hosted service and the service is shared to a group or its private the username will show up in the editor tracking fields. If you are using an ArcGIS Server service you will need to token secure it and set up a user & role for that will be applied against the service. When you open up the map you will have to authenticate against that layer and the user you do that with will show up in the Editor Tracking fields.
Has this changed recently?
We have secured services from ArcGIS Server that require a username and password to connect to the REST endpoint to obtain a token. As you indicated - the token user was the name that was written to the editor tracking layer with Collector - not the AGOL user.
Testing today would indicate the AGOL user name is now written into editor tracking field.
Can you explain how to " set up a user & role for that will be applied against the service"
With the option "Users from an existing enterprise system (LDAP or Windows Domain) and roles from ArcGIS Server's built-in store" I am able to use Active directlroy users, and when I open the map the Feature Layer shows and it is editable.
but with the option "Users and roles from ArcGIS Server's built-in store" I already created an user in ArcGIS Server, but I can not log it, it shows the error message: "Unable to access the authenticated service"