It's wonderful that you've been able to give up potatoes & rice in favor of salads & protein. Kudos! I'm still amazed about how much of a carb junkie I was & that now I don't crave them at all.
The ADA gets a lot of funding from pharm companies. More carbs=more meds & insulin. My experience has been that large, powerful organizations & their highly paid leaders become more concerned with their continuing survival than they do advocating for the constituency they allegedly represent. They may not have started out this way, but power/money talks. They become an institution & institutions are painfully slow to change.
I'm not a doctor or a biochemist, but it has never made sense that people with diabetes are advised to eat foods that we can't handle. All I know is my own experience, which is borne out by others. As soon as I rejected the ADA guidelines, shoved down my throat by my doctors, CDE, diabetic ed class & nurses, I immediately felt better & had better BG. It's simple. Cut carbs, less insulin (or meds), better control.
I've heard various theories about why low carb isn't promoted, other than the obvious that beliefs are slow to change. One is that our diet has been so carb heavy that people would be unwilling to change & that no one would follow a low carb diet for long. Doctors assume people won't do this, if they even believe low carb is helpful. Of course, this places the power of our health in the hands of others who gatekeep info & treat us as children assuming what will, can or can't do. Others, due to incorrect info, believe that low carb is dangerous. I've been told by several healthcare professionals that low carb would harm my brain. Welcome to the dark ages:)
My sense is that low GI isn't a good tool for diabetics. There's been virtually no reseach that I can find that shows how GI effects diabetics. Slow or fast, carbs hit us hard. Foods that are high carb, regardless of GI, begin to turn to glucose as soon as they're chewed. You've experienced this from your own experimentation. Enzymes in salvia start the process. If certain low GI foods do hit later, in a way this makes it even more difficult for people with Type 1. I don't want glucose hitting my bloodstream after my injected insulin is already gone.
Really don't know if GI is being kept from the US public intentionally, or if it's just slower to catch on. I've seen discussions here about GI, so I think it may be more prevalent in the US than it seems.
There appears to be a lot of variables in what constitutes the GI of foods--cooked, uncooked, ripeness/freshness of the food, individual biochemistry on how we each handle particular foods--that make it difficult to really assess GI to begin with. GI is based on averages of how average people process food. Just my two cents, but I think it's a whole of smoke & mirrors & just the latest diet trend. One thing that bothers me about GI for diabetics is that it helps justify a high carb diet. Hey, it's low GI, so eat what you want. It doesn't factor in that a BG spike now, or later, is still a spike.
One of the TuD members (Craig) has written extensively on his success controlling his Type 2 with mostly raw foods. You'd enjoy reading his posts.
Vegan is difficult, if not impossible, to do low carb. It's carb heavy/lower protein. A person could live eating very low carb because protein eventually turns to glucose, but our bodies have to have a certain amount of protein to survive & vegan protein sources are high carb. As a Type 2, you might be able to do this. Yep, YMMV. Whatever works well for you is the way to go.
I was a vegetarian for decades before being diagnosed. It was so hard for me to begin eating animal protein. I tried being vegetarian again & I just couldn't handle it without huge doses of insulin. Huge doses means the margin of error of matching insulin to food is correspondingly high. I was high, I was low. My BG was all over the place & I felt like hell.