So, to me, that does seem like it's a bit more than one would expect from an immediate post-op diet. That said, I only have my own experiences from which to speak and if this is the diet that your doctor prescribed, then they may have a reason.
For comparison, here is the diet I am on currently (I hit 10 weeks post-op tomorrow), which is not really standard for most programs that I've seen:
2 times a week:
Breakfast - 9am - 2 scoops of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (185 calories)
Lunch - 1pm - 1 scoop of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (115 calories)
Snack - 4pm - 1 protein bar (18-20g of protein -Think, Pure Protein, or Built Bar) (160-230 calories)
Dinner - 7pm - 1 protein bar (18-20g of protein -Think, Pure Protein, or Built Bar) (160-230 calories)
60+ ounces of water (usually Crystal Light) (40 calories if all Crystal Light)
1 time a week:
Breakfast - 9am - 2 scoops of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (185 calories)
Lunch - 1pm - 1 scoop of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (115 calories)
Snack - 4pm - 1 bottle of Premiere Protein protein water (20g of protein in 16.9 ounces of fluids) (90 calories)
Dinner - 7pm - 1 protein bar (18-20g of protein -Think, Pure Protein, or Built Bar) (160-230 calories)
4 times a week: (up from 3x/week as of this week)
Breakfast - 9am - 2 scoops of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (185 calories)
Lunch - 1pm - 1 scoops of Celebrate 4-in-1 in 8oz of unsweetened almond milk + 2 tsp Benefiber (115 calories)
Snack - 4pm - 1 protein bar (18-20g of protein -Think, Pure Protein, or Built Bar) (160-230 calories)
Dinner - 7pm - 3-4.oz of allowable soft foods (I've had ground chicken, ground turkey, pureed chicken salad made with hummus & greek yogurt, ricotta bake, baked/steamed whitefish, scrambled eggs) (210 - 250 calories)
So I think there would be room to make adjustments to your diet plan, as long as you would still be hitting your protein goals, but that is definitely a conversation you would want to have with your doctor. Simply be upfront with them about your concerns about the slow weight loss and ask for guidance on how to make changes to your diet plan to facilitate better results. Some times you have to make those changes to the diet plan in order to keep your body on it's toes!