And thanks for bringing this up. There's actually a fairly active conversation happening internally about this same exact issue. In short, though, the underlying OpenAPI connector that powers the resource doesn't support file uploads. We're already planning a refactor that will unlock this functionality, but it's unclear when that project will be finished. In the meantime, you can alternatively configure a dedicated REST API resource similar to what is shown here.
Let me know if you have any additional questions! If you want to talk through the alternative that I mentioned above, you can always join our Office Hours.