The Short Answer
DULCI isn't a sweetener. It's a prebiotic fibre supplement, classified as a food, where fibre is the main ingredient by weight and the thing the product is actually for. The confusion is understandable: a sweet first taste makes it easy to assume a sweetener with fibre added on, rather than the other way around.
What DULCI Is
DULCI is an excellent source of fibre by the regulated standard: one 8.5g scoop gives you 7g of fibre, clinically studied prebiotic fibre specifically. It's Low FODMAP, certified at ingredient level, Gluten Free, Plant Based and Non-GMO, with a 5 Health Star Rating. Fibre is the subject of the product; everything else about it describes how that fibre shows up in food and drink.
What's in a Serve
Two ingredients: the fibre itself, and stevia. One 8.5g scoop gives you 7g of fibre, which is the figure the fibre's lab testing is allowed to declare under Australian labelling rules; the rest of the scoop's weight is the part of the fibre ingredient that method doesn't count, plus a trace of stevia.
Why It Tastes the Way It Does
Stevia is the second ingredient, present so the fibre tastes like sugar rather than tasting like an unflavoured supplement. It's there to make the fibre easy to use in the things you already eat and drink, not the reason the product exists.