I think part of the confusion is that we're treating the topic as though there is one issue. I have Elana's book b/c I use almond flour. As a diabetic I can tell you for a fact various "safe" foods drive up my blood glucose. Fruit & wheat to name two. Honey & similar sweeteners are out of the question for me - but not "normal" people.
We are discussing 'good sweeteners' as though they are good for everyone. Concentrated fructose is certainly not what I consider good food nor is it good for everyone. But limiting servings might keep you in a 'good' range... unless you cant tolerate fructose or don't have the detailed info to calculate consumption. (Agave comes mostly from Mexico & the US does not regulate production. We have to trust what is on the label - details are important).
Testing had not been done previously with diabetics and agave. The institute's study does not draw specific conclusions b/c they have not tested for the most likely culprits such as serving size. EX: Oat meal is considered both "good" and "safe." If I eat one pkt my after-meal bg is OK. If I eat 2 pkts my bg skyrockets.
Let's be realistic: table sugar is fructose & glucose - as are honey & agave nectar. There are pros & cons for each due our tastes, processing methods & specific composition. But it w/b cruel to continue to certify something as safe for diabetics when that is not certain.
I'll continue to use stevia as my primary sweetener. Not a sugar; no carbs; glycemic index of 0. I'll also use xylitol, approved by the Amer. Dental Assoc., even though it is an alcohol sugar b/c it helps fight bacteria & does not raise my bg. I can calculate the serving sizes of these ingredients.