The major problem isn't that you now have to ask the user for access for a specific folder, but that you're also stuck with the Storage Access Framework's APIs

The major problem isn't that you now have to ask the user for access for a specific folder, but that you're also stuck with the Storage Access Framework's APIs afterwards, which are somewhat less than satisfactory to use (see also https://news.ycombinator.com/item?id=19525092 https://news.ycombinator.com/item?id=19525092), don't play nice with native code, etc. It would be a different thing if the user picking a folder would also offer a way of giving you regular file system access for that part of the storage.