I don't think the dialogue supports the reality collapse idea:
AO: "The Infinity Stones create what you experience as the flow of time. Remove one stone and that flow splits. Now, this may benefit your reality but my new one, not so much. In this new branched reality, without our chief weapon against the forces of darkness, our world will be over run. Millions will suffer. So, tell me Doctor, can your science prevent all that?"
BB:"No, but we can erase it. Because once we are done with the stones, we can return each one to it's own time line at the moment it was taken. So, chronologically, in that reality, they never left."
AO:"But you are leaving out the most important part. In order to return the stones, you have to survive."
BB:"We will, I will. I promise."
AO:"I can't risk this reality on a promise. It is the duty of the Sorcerer Supreme to protect the time stone."
Banner does use the term "erase" but in the context of preventing a bad future in the new timeline, not erasing it from existence.