For a general definition of relevance, we can use the following which is due to Hjørland Sejer Christensen.
Something (A) is relevant to a task (T) if it increases the likelihood of accomplishing the goal (G), which is implied by the task. With this definition, the relevance is related to the task, but in strategy we need something more specific. To do this, we need to codify the task as a strategic mix in order to be global and not only local. So, the relevance has to do with the efficiency of contribution in this context. If the contribution in the strategic mix is negative, we say that it is not relevant. So the relevance is the positive contribution in the strategic mix. But this can be passive and not active. In the last case, which means active, we say that we get a strategic relevance. In fact, we have then the frame of cooperation. So the strategic relevance is related to the notion of cooperation. To be more specific here, we can make a distinction between a cooperative and a synergistic behavior. The first one is a positive collaboration and the second an efficient collaboration. The strategic relevance can be strong in the context of a synergistic behavior. In conclusion, the concept of relevance and even more of strategic relevance is not independent of the task and it depends on the strategic mix. And in a case of an application in reactions, we have to consider this as a condition and not as a result, to obtain a specific goal.