I have not tested the behaviour with all workspaces, but am puzzled by the way it works in the Records Window.When enabled, the Property Box always displays the record details for the currently selected record (that is the record currently selected in the active workspace window).
The following seems to happen whether or not sync is enabled, so the sync is having no effect:
If a new selection is made in the currently viewed tab of the Records window, or a new selection is made on switching to a different tab, by making a single click on the required record, in each case the record will be highlighted in blue and the Property box switches to that record.
However if you switch to a different tab where there is already a previous selection highlighted in blue, the Property box does not switch to it, and a single click on the selected record has no effect. A double click is required to switch the Property box, but then the selected record is highlighted in grey. A further single click is required to turn it blue again.
A further question is why, when an already selected record is double-clicked, does the highlighting turn from blue to grey? This seems to suggest it has been unselected, but this action is needed to switch the Property Box to that record.
In case it is relevant, in Tools> Preferences > Records window I have selected Double-click on record in Record List means ‘Open Property Box’.