Yes and no for example if reliable source A calls incident X state terror and uses argument Y to prove it then a separate reliable source B that supports argument Y might be used even if it doesnt directly speak of state terror Likewise if reliable source C criticizes argument Y again with no mention of state terror they we can also use it Also even when there is no controversy perse you might want to use sources that provide supporting information such as proving the existence of organizations or laws Your perspective I am afraid is a narrow one  In other words while the narrative should be around precisely source who do explicitly use the term there are many instances where sources can and probably need to be used that do not explore the concept itself Lastly even when the phrase state terror is not used but the article is clearly about the topic it might be included Rather than a blanket prohibition in the abstract we should have a discussion on inclusion in the concrete for each instance