If you crate a view grouped by Start Date (with 'Group only by Days' on), you can move tasks by drag and drop, which is really handy. I use it all the time with Due Dates. The trouble is, moving a task in this way treats the task as if it were set to 'Lock Period' - ie it moves the due date too, regardless of whether 'Lock Period' is set or not. One time it even removed the due date entirely (on a task that was originally set to inherit dates from it's project).
It's such a useful feature on Android, but it needs to act in the same way as changing the start date does in the properties screen - ie has no effect on the due date unless 'lock period' is set.