Hi I haven't started my pre-op diet yet, but I do understand some of the reasoning behind this. So my geuss is partially your doing shakes to adjust to the diet you'll have to follow afterward. 96 carbs is still considered low under 100 is low. Take a diabetic diet 15 carbs are considered one carb exchange. So, your getting one carb exchange per meal. The shakes are also low fat, but what about fiber and protien. The protien is to balance out the carb intake. If there is any fiber that is subtracted from the carbs. Anyway some people have had there surgery put off due to a fatty liver. And from the sounds of the shakes they should help with that.
Try to stay positive this is a life change three weeks may feel like forever but it really is not that long. If it bothers you so much call your doc and ask if there is another way.
God bless you in your wieght loss journey.
Nora