Yeah, I was actually wondering why that's the case, or if it's just a matter of only glucose being measured in the glycemic index.

But on the Wikipedia page for fructose, it says this:

The liver converts most fructose and galactose into glucose for distribution in the bloodstream or deposition into glycogen.

So, I'm guessing, that's what 'slows' it down and makes it healthier in that regard.