Product Owner should not typically be a full-time position on its own, but rather a role played by someone on an agile team. Usually, but not always, by the product manager. In other words, it is a subset of a product manager's responsibilities which would also include cross-functional stakeholder and go-to-market activities that normally don't fall under the "product ownership" umbrella in the Scrum sense.
It's called Product Manager now
and 9/10 companies still think a project manager is a product manager :D
I also agree. And I sometimes suspect it has something to do with abbreviation of both are the same (PM).