Currently Attribute Template Editor and Attribute Editor behave different regarding visualisation of templates when using derived templates.
Attribute Template Editor shows the attributes of the base template only if Group By Template is checked.
Attribute Editor always shows all attributes independent on which template the attributes belong and independent of the group-by-state. When you check Group By Template the templates get visible.
I think it would be a great to see all attributes also in the Attributes Template Editor, independend of the group by state. Maybe all attributes of the base template should be grayed out.