I would get some ketone strips at the pharmacy and test urine for ketones.

Any surgery is going to raise blood sugars but those high blood sugars need to be treated, not only because they are toxic but because they affect healing and even infection. If it was a GI specialist who said it was "normal" they may not know much about diabetes and blood sugars. To be honest it has been our experience that many providers outside of endocrinology are too accepting of high blood sugars. They need to be managed, not accepted. Very high blood sugars like 400 can cause some of the symptoms you posted, both directly and indirectly.
https://www.verywellhealth.com/after-surgery-infection-and-glucose-3970391#:~:text=The%20stress%20of%20an%20operation,%20along%20with%20potential
How Uncontrolled Levels Impact Surgery and Recovery
Blood sugar that's even slightly elevated can lead to delayed healing and increase your chances of getting a wound infection from less than 2% to almost 18%. In general, the higher the blood sugar, the higher these risks.3

Additional risks include:

Slow or poor wound healing
Fluid and electrolyte imbalance
Kidney issues
Heart and/or lung problems
Neurological complications
Stroke
Post-surgical death1
This increased risk is why the hospital may check your glucose frequently as you recover from surgery, whether you have diabetes or not.

Post-Surgery Management Tips
Your diabetes needs to be well controlled after your surgery as well to prevent complications such as wound infections, slow healing, and increased scarring.1
Duggan EW, Carlson K, Umpierrez GE. Perioperative hyperglycemia management: An update [published correction appears in Anesthesiology. 2018 Nov;129(5):1053]. Anesthesiology. 2017;126(3):547–560. doi:10.1097/ALN.0000000000001515

If you're not consistent about taking care of yourself, taking medications as prescribed, and routinely checking your glucose levels, seek help from your healthcare team. They can work with you on an effective treatment plan.

A lot of factors can make it difficult to eat regularly while you're in the hospital, such as vomiting, lack of appetite, stress, or pain. If you're not eating well or if you've been prescribed medications that may increase your blood sugar, you may need to stay longer for blood-sugar monitoring.11

Keep in mind that the following are essential to a quick and healthy recovery:

Eating appropriate foods after surgery (whole grains, fruits, vegetables, and lean protein)
Frequently checking your glucose levels
Taking your insulin or other diabetes medications as prescribed