I think we have been here before!
I do have the same 'reaction' as you when I eat carbs, sugars, grains dairy, etc.
The only element that is notably different is that you spike later than me!
In fact, by the time you spike I'm already slowly coming down.
I don't crash as such, I just keep producing insulin slowly but surely until I eat again and it has to be low carb, to restrict the production of more insulin.
I am eating very low carb and intermittent fasting to keep my body as insulin free as possible. My trigger (carbs and such) is one that has an overabundance of cells that trigger insulin. My 'off switch' is abnormal.
I think you do have a form of hypoglycaemia, and having discussed with hypoglycaemic sufferers, none of us are similar in how we react and what triggers and the time it takes to spike and hypo is different.
The closest I've seen is a patient with my endocrinologist, who has similar on a graph except at the hypo stage, where I went below three fifteen minutes before the other patient. Both had similar spikes and the drop.
This was a prolonged OGTT.
I haven't had a hypo for over two years now, my control is very good and I believe that the gliptin inhibitor I take, helps as well!
See post below. I have another autoimmune disease only found with people who have the "hunter" gene. We get fatigue which can be controlled by never letting our blood sugar go to high (not defined at present). People with the "hunter" gene do not create insulin until their blood sugar rises. This is great for famines. Women with this gene have problems controlling blood sugar with pregnancy. People with this gene tend to get fat (not inevitable) with the modern diet. I do not know the other problems with this gene which must exist because it is only prevalent in the near east (falling monsoons) and possibly with other populations which go from a hunter type life style to the modern world.