why does the rings of power page spoil a character mystery?

hello, https://www.imdb.com/title/tt7631058/ this page contains a major spoiler for a mystery character. right at the top of the cast list, it identifies a character, as having a different name to the name they are given when we first meet them. (in fact for the ENTIRETY of season 1) I have not seen this show before and avoided any media coverage so I did not know about this plot twist. I was under the impression IMDB respected the presentation of media and the plot development including surprises and mystery elements. Surely this must be an error? In any case, this has severely damaged the enjoyment of this show for me.