Altium Designer 16: Baked symbols in schematic templates
After some testing, it has become apparent that a distinction is required between:


The *.SchDot file that is used as the drawing backdrop template, and
A *.SchDoc file that is used as part of a PROJECT template


The former "bakes in" everything as a permanent fixture, whilst the latter permits the inclusion of components as per any normal schematic.

The solution to my above issue was to remove all components from the *.SchDot file, and use it to contain only drawing objects, such as the title block.

Any components to be added to all boards as a matter of procedure were included in sample *.SchDoc files, as part of template projects.