What is the use of FileSystem API in Firefox?

Are there any use cases of using File System API in Firefox? All examples on MDN show savePicker functions that are not supported by Firefox. Can you use this API for something useful or is it useless in Firefox?

I’ve found requestFileSystem but it’s deprecated and not supported by Firefox.

I want to play with the API and maybe create FS library or extension to lightning-fs for usage with isomorphic-git.