Thank you for your answer - that helps me understand the complexity. The only point I want to make is that this issue affects macOS Catalyst apps, which do need this use case. I tried to use a AppKit plugin, but the problem is that the URL from the UIDocumentPicker is an iOS-based URL and the method is still not called in that case. If you know of a workaround using an AppKit plugin, please share it. Thanks.

This also affects Catalyst apps. I have filed FB15776793 with a sample app.