Here are the results of my tests on a Pixel 2XL (Android 11 Beta):
android:targetSdkVersion="30"
As shown in this video, when I save a text file in
- the Private directory or
- in the ASD
it doesn't work with the File component without WRITE permission. But it works with the EFile extension (as it should!).
In addition, if the first button (copy dummy.txt ...) is clicked, you get this error, although the file was saved correctly (in the Private dir, and not in the root dir of ext. storage):

To check this on your Android 10, 11 devices:

