Mini-gastric bypass is not a standard of care bariatric operation and is not covered by any insurance policy that I've ever seen (and since I help people with insurance appeals I've seen A LOT of policies). There is, to my knowledge, only one group in the USA doing it. The big problem with it is that it can easily cause severe problems with bile reflux, which is not treatable with antacids because bile is not an acid, it's a base (the opposite of an acid). And bile is very damaging to the esophagus.
I get that you are still exploring all your options, but you are looking in the wrong direction on that one.
On your policy, it is sadly outdated. Almost no one is doing VBG anymore because if the high failure rate. There are probably one or two old guys still doing it, but that's about it. It used to be a standard of care operation but isn't anymore. Yet your policy covers it. Sad.
I think like
@southernlady that you should pursue whether or not the DS is covered. It is not the same as the BPD and just isn't listed on your policy as covered or not covered. Again, a very outdated policy! But it is a standard of care operation and has been for many years now. Keep trying.