As for the clear workaround, "creating changeset in P4V" Yes, that is possible. That works for one person, because they know what to do. What happens if you need this integration for a whole team of people? Suppose a use case: Someone on a large team is making a change to a file that needs to be added to their changeset as soon as possible. I'm making a tool in the Editor that does exactly this. If they use the tool to edit a file, it will create a changeset that they can name within the editor and it will go in P4V.
Instead of me telling everyone on the large team about this, that if you edit these files, they need to be included in their changeset right away, it would be so much easier for me to automate this for them.
To accomplish this, I'm using an Editor script to run a cmd line process and use the p4 command line interface to create a changeset for this functionality, instead of simply using the Provider integration within Unity. And that seems ridiculous. Especially when your reasoning for not fixing this are based on assumptions. Using words such as "likely" and "seems" means that you did very little investigation.

If the Perforce Provider integration is not supposed to create new changesets, then why is this function named this way in the Provider class?
"CheckAndCreateUserSuppliedChangeSet"
"Create User Supplied Changeset" What would that mean other than that it would create a user-supplied changeset, one that has not been created already?