It's not bad character development at all. My theory is just that. The cuck idea is an extremely hypothetical scenario at present, which the Devs have never suggested is going to happen. So if he's not going to be cucked, why would they do it? Until if/when that becomes an option, nothing like that is going to happen. Because that would be giving the game away, and if there's one thing we know about Deep, he doesn't give anything but the vaguest clues of what's going to happen in the future.
In the first choice, where Anna decides to split up with him, she does say, but I don't need to say anything until I decide to cut and run. And the clear indication of that, is nothing is going to change between her and Andrew for some considerable time. Andrew's purpose in this game, has always been to be the guy she cheats on. Deep told us this years ago. He's always been clear about that. And as such, he cannot find out the truth about Anna. Andrew was created to be the fall guy. And until Awake joined as a joint Dev, that was all he was going to be. Deep fully intended to have Anna dump him eventually. But Awake persuaded him, to give Andrew an ending with Anna. So that will be the vanilla ending probably. And if he was to find out now, well that couldn't happen. He'd have to have, two completely different Andrew paths. One where he knew, and one where he didn't. And that would delay things, and we don't want anymore unnecessary delays.
So just in terms of practicality, I don't think it would be sensible to do what you suggest.