MacOS Big Sur File permission grant changed, How it is?

Before macOS Big Sur, my app popup an NSOpenPanel and let users select "/" for grant full access permission, but now it's not working.

If NSOpenPanel grants the root Directory "/", It's no effect for its subfolders like "/User/Tom/Documents".

And worse that I don't know how to trigger System grant access popup alert, So my app never appear in Security & Privacy -> Privacy -> Files and Folders

How these works, who can give some help to explain, thanks