Comment 1 for bug 1836499

The documentation is a little bit confusing here -- the "HintSystem" property is not about the device access or filesystem permissions, it's about "accessing" UDisks functions using PolicyKit.

See the policies here [1] for mounting filesystems -- "normal" devices can be mounted by a "regular" user (in an active session), but "system" devices require root authentication (similar policies exist for unlocking encrypted devices, ejecting drives etc.)

[1] https://github.com/storaged-project/udisks/blob/master/data/org.freedesktop.UDisks2.policy.in#L15