It's mostly about washing food through allowing you to eat more. There is a lot of the same rules with RNY.
Food and drink volume restrictions are about stretching. So stick with your Doc's rules on volume.
While the times when to stop and when to start vary with Docs, as you indicate, they work to achieve the same thing. Some Doc's overcompensate, some give the minimum reasonable. Doc's also learn what to say based on what past patients have done. OH, also remember that Doc's don't do the same surgery in the exact same ways, so there is variation. So rules may be different between Docs for very good reasons. Just a thought to ponder.
So, for 6 months give your Doc the benefit of the doubt. After all, you trusted him to move your insides about.
As you get MUCH further out, as a natural course of things, you will test what happens if you shorten or lengthen the times. You may even... horror of horrors... test drinking with meals. But, knowing WHY and WHAT the Doc is working to achieve with your rules, stick to them in some way that honors the intent.