Well, the idea of conventions is that people agree to use them. I see a lot of variation in the degree to which people know about or are attached to this one.
While there may be a set of textbooks and papers for which the editors would have flagged "worst cast O(..)" as redundant, I think it's relevant to point out that the use of big-oh notation in mathematics predates computer science. So to the extent algorithm analysis is a branch of mathematics, those who use big-oh in this more general way are in fact consistent with the larger body of work.
While there may be a set of textbooks and papers for which the editors would have flagged "worst cast O(..)" as redundant, I think it's relevant to point out that the use of big-oh notation in mathematics predates computer science. So to the extent algorithm analysis is a branch of mathematics, those who use big-oh in this more general way are in fact consistent with the larger body of work.