Ok, I never really got a answer to this question so its been sitting in the back my of my head for a long time. I’ve stumbled across a plausible explanation

The Randall cycle : A cross inhibition between glucose and fatty acid metabolism in every cell. When both high glucose levels and high fatty acid levels exist at the same time the Randle cycle causes the cell to rapidly fluctuate between both method, which does cause stress and inflammation in the cell… now some handwaving… this is manifested as insulin resistance (i.e. the cell can’t update more glucose because of the Randle cycle inhibition)

Now… this is a CROSS inhibition… so if you remove one of the sources (glucose, and fatty acids) then the Randle cycle just stays in one mode and you don’t get the seesaw inflammation.

This would account for the all starch diet being able to fix insulin resistance (no free fatty acids). It’s a mechanistic explanation that works for me. i don’t understand it fully, but it seems to fit.

Obviously going all glucose isn’t super healthy, and I wouldn’t recommend it, but it has been a puzzle on why it works in some circumstances.

i.e. https://www.youtube.com/watch?v=OlsjnLMANDQ