Well that's both fair and true. I think it's a good thing that some people are completely unattainable, it is as you say, realistic. It's less that I'm concerned about Eder being player unromanceable (I don't personally care either way, just got nosey with the game data and thought that tidbit was interesting), but it's at odds with previous information given by the character. His whole thing with rejecting the Watcher is either "I'm really sorry but I don't like men" for male watchers, or "I haven't even thought about any romantic relationships for years, so that's why I haven't even tried to think about you that way" for female watchers. Not direct quotes ofc, but those are the points he lays out.
And then he potentially goes and hooks up with someone who is at best an occasional consciousness in a man's body, so he was either lying to the watcher about his reasons (which is a mean thing to do to someone you respect) or he has been inconsistently written, both of which some people may see as narratively frustrating.