Is it reasonable for us to agree that, when someone uses a pseudonym, he or she, for whatever reason, chooses to mask his or her real identity?
No, I don’t think we can agree on that. The range of possible uses of pseudonyms is far more complicated than that. For instance, there are cases where the author claims to merely be a transcriber, and attributes the creatorship to another name. The author is not masking their real identity, because it is easy to discern the truth. It is merely an artistic expression. But if we catalog the work as it presents itself, without clarification, we may do a disservice to our users. There are other cases where the author is not seeking to mask their identity, but to create an artistic sense of separation, or to make distinctions between categories of works, while openly embracing their creatorship.