I think this is what we call a "Twist". We all speculated that this was the one thing that Tanveer can bring up to cause a rift between Sanam and Aahil. Tell Aahil that once he tells Sanam he shot his Father, she will struggle to accept a killer.
But that is NOT what happened at all. Aahil has come clean with his wife. So the only trump card that Tannu had was making him feel insecure about his ability to be a good husband. Make him believe he has lived too fickle to ever commit to anyone. After all, when you own MOTHER tells you that you cant be a good husband, you start to doubt yourself. Also, when she says it under the guise of "Don't ruin Sanam's life" and guilt's him, he feels like he really should exercise caution.
THIS twist is going to be Billi's downfall. She has NO idea that Aahil has already given his version of events to Sanam. So Billi gives her HER version and Sanam realises that they are not the same, and correctly smells a rat!
That scene was shot at the same time as the Balloon scene. Same clothes, same lighting etc. It was NOT shot later. It's clear they kept this scene in their arsenal to use later. Just like when Sanam told Aahil not to drink. The scene where he throws the alcohol into the pool was not there in the original, and later we are shown it. So this is exactly the same thing. It was not bad editing, or an afterthought shot later. It was always part of the plan.
But what I want to know is where are the guys? No Rehan, and only 2 minutes of Aahil. I know KV had a promotion event for his movie? But Shehezad seems to be on holiday coz he has not been in any episode since Tuesday?