Following on from: Bug 358085 - Regression: Device Notifier ignores the setting of "Removable Devices Only" The Kernel, as from v4.4.x now supports hot-plug on SATA devices. This results in hot-pluggable drives being shown as "removable" in "sys/block/sdX/removable". OK, in the broadest terms a hot-pluggable drive is removable... It is from "sys/block/*" that "udisks2" derives it's information, and udisk2 is where Device Notifier derives it's information. There is a bug report ( https://bugzilla.kernel.org/show_bug.cgi?id=111651 ) against the mainline kernel regarding this issue, but I'm not sure it's being treated as a bug per se. As I understand it, later BIOS may have the ability to disable (I assume the reporting of) the hot-plug status. Older BIOS may not have, or the hot-plug status is simply "wrong". With regard to the Device Notifier: An option per device to ignore that device would be a good solution. At the moment having what are essentially fixed devices appearing as removable is not particularly good; "dangerous" even, as one could inadvertently un-mount the device.
The stable kernel switched to 4.5.0 and contains the fix for this problem: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=dc8b4afc4a04fac8ee55a19b59f2356a25e7e778 ata: ahci: don't mark HotPlugCapable Ports as external/removable The Device Notifier no longer shows fixed (HotPlugCapable) devices as removable/ejectable.