This is where I am with Will Smith. Ya, I joked about him being a cuckold the other day, but we all know this is the truth. Smith can talk all the game he wants about being in an open marriage, but he was straight-up emasculated when Rock barbed in her direction. It all came rushing to the top.
Will is...you know..."enjoying" the open part of his relationship too. This isn't cuckoldry. It's just modified swinging.
The problem is more that he didn't want people to know that they did this, because of the overall perception of other people effing his wife. Which, like you said, resembles cuckoldry. So yes he absolutely felt emasculated. And that's why I feel bad. He wanted their (perceived as) odd relationship out of the public eye, and August/Jada refused to let that happen. So now he's talking about it at length, even though he has no desire to.
I think there's a ton of room to blame everyone involved. August for spilling the beans, Jada for leaning into the publicity and talking about it, Will for lacking control of his emotions AND trying to talk through his emotions in the public eye, AND Rock for the obvious tasteless joke.