This was done silently and caught a large number of users off guard when updating their shiny tablet from 3.1 to 3.2. While in 3.1 they could use the file managers to write random files to the card in the slot, 3.2 just gave access denied errors. And this even tho the UNIX rights looked ok.
The workaround seemed to be to go via the MediaStore database, the supervisor of the MTP implementation in Android, and in essence pretend that the file came from a computer attached via USB. But even when done that way, you could not delete files, or directories, once created...
Never mind that said database had a bad habit of getting silently out of sync if you used a file manager on the internal storage area (that infuriatingly still carried the old RW permission system, confusing users even further towards thinking the issue was a broken SD card rather than Android changes). Meaning that what a computer would see via MTP, and the actual state of the Android device, may not line up at all.
And i fear that future Android changes will likely bring more of this, thanks to the policy that the user should not touch the FS.
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