As someone who left iOS for Android because of that, I was pleasantly surprised - when I went back - to find that iOS now has a Files app for managing files on the device and also network shares.

iOS has definitely improved in that area and definitely now has a filesystem.

As someone who regularly uses vim inside iOS to edit files from another application and syncs the whole lot via SyncThing, I beg to differ.

From a filesystem perspective, it's no different from jails or container mount points.