From what I gather, the focus of PyOxidizer is on enabling you to create executable Python binaries which embed a Python interpreter rather than providing Python packaging and dependency management.
These two are totally different tools, not even comparable. With Poetry, you handle dependencies, just like with npm, cargo or pip itself. PyOxidizer can build a standalone binary which doesn't need an installed Python interpreter, so you need both.
https://python-poetry.org/