The basic difference there, though, is the TheBF acted on his feelings. My ex didn't. Imagine if the TheBF had started telling everyone you were married but without any intention of actually getting married and without consulting you that he was going to lie like that.
The social pressure on my ex was in his mind, and his 'solution' was fiction too - I did put his needs ahead of the truth and go with the lie. I now consider that a bad call, I feel I let myself down and that, ultimately, indulging his paranoia like that was letting him down as well.
I see your point, but I don't think you should be so hard on yourself. You obviously cared about his feelings and his self perception, and he put you in a difficult spot in regards to having to choose between his feelings and your own. I am like you and I think I would have done the same thing, even if I ended up having the same regrets.