I draw your attention to the following tags on Meta: scope and allowed-topics.
scope is on 52 questions, has a tag wiki and excerpt.
allowed-topics is on 18 questions, with no tag wiki or excerpt.
Further, "scope" is more-or-less a standard tag on Meta sites. Examples: Meta Stack Overflow, Meta Stack Exchange.
They cover the same ground. As scope is older, has more questions, has a wiki and excerpt, and is a de facto standard, it should be the master and allowed-topics should be a synonym of it.