I read somewhere that choice paralysis hits way harder when the options look almost the same, and that's exactly what happened with your ghost border vs dark mode thing. We had a similar mess where someone made a "danger" button in three different reds, and nobody could agree which one was the real one. Ended up printing out a one page cheat sheet and taping it to the monitor, but even that didn't stop people from saying "oh I thought the lighter one was for warnings". Also, your 12 unused variants thing is spot on, I've seen teams keep buttons alive just because one senior dev vouched for them once in a meeting three years ago.