When the stomach is wrapped and stitched, it creates pressure on the LES and strengthens its ability to stop acid from refluxing.
I found this quote which seems quite simple to understand:
"Then, whenever the patient has something in his or her stomach, the pressure
generated is transmitted to the collar wrapped around the esophagus, compressing
the esophagus further.
"Therefore, the more pressure inside the stomach, the greater the pressure
inside the esophagus."
For a fairly common procedure there's not a lot that really explains the way the wrap actually works. My surgeon told me that more than a valve, the wrap is a one-way flap that lets food and drink in but stops things from leaving the stomach and entering the esophagus.
I believe the stitches stay, but the scarring/healing of tissue is what gives it the strength it needs to withstand all the pressure we put on it both with moving and eating.
The reason it starts working better after healing progresses is because the swelling recedes and the wrap settles into place better.
Hope that helps.
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”