Should Stackelberg Mixed Strategies Be Considered a Separate Solution Concept?

It is sometimes the case that one solution concept in game theory is equivalent to applying another solution concept to a modified version of the game. In such cases, does it make sense to think of the former as a truly separate solution concept, or should we entirely subordinate it to the latter? The answer probably depends on the particular circumstances, and indeed the literature takes different approaches in different cases. In this article, I consider the specific example of Stackelberg mixed strategies, and argue that it makes sense to regard these as a separate solution concept, even though a Stackelberg mixed strategy can also be seen as a subgame perfect Nash equilibrium of a corresponding extensive-form game. The analysis of this special case may have implications for other solution concepts.