I know this has been discussed before...

The goal isn't to have the protein sit for as long as possible in your tummy.  Why would that be the goal?

I don't know if I would call it a goal.... more of a strategy would be more accurate.

The sleeved stomach is "known" to empty about twice as fast as a normal stock un-altered stomach, generally in about 45 minutes vs. 90 minutes.

The strategy or goal for slowing down this process is to eat dense protein, close the pyloric valve and hold food in there for a longer period of time.

"We" most likely associated satiety before as a full stomach and something in the sleeve is most likely our main association with satisfaction. 

There is another learned strategy with recognizing satiety after the food passes into the lower intestine, but that's another subject.

So it is a good strategy to keep food in your sleeve for a longer amount of time.

A major component to the VSG is the restriction, you get the restriction by eating dense protein and not slider type foods.

Hope this helps.

frisco