State of the art treatment these days (at least in artificial pancreas land, where I spend all of my time) is more focused on sensitivity-agnostic treatment; figuring out the insulin sensitivity dynamically rather than trying to control the sensitivity itself (it's much more multifaceted than a few hormones, we're talking hundreds of possible ways it can change).
Also, and I'm sure the authors would acknowledge this, n=32 is enough to demonstrate a possible effect, but not nearly enough to show this effect in the population at large. You usually need n~5000 or more for such effects to be shown generally, though the actual number depends a lot on the drug and what you're trying to treat.
We're conducting our first human study at a world renowned US diabetes center soon, I'll see what our PI thinks of this work. Thanks for sharing.