Of course it's (normatively) wrong. But if that particular error is what's going on in peoples' heads, it'll manifest as a different pattern of errors (and hence useful interventions) than an availability bias: availability bias will be cured by forcing generation of scenarios, but a preference for oversimplification will cause the error even if you lay out the various scenarios on a silver platter, because the subject will still prefer the maximally simple version where A->B rather than A<-C->B.