Meh. I tend to take anything from Paula Begoun with a pretty big grain of salt where hair care ingredients are concerned. Her research has always seemed to me to be oversimplified sometimes to the point of being inflammatory and misinformative, and often comes with an agenda (like her advocacy of the use of silicones in hair care products because she uses them. )
I think part of the problem is the various uses of the word humectant itself. It's often used in different ways, to mean anything from "moisturizing", to "attracting water" which to me are contradictory, one implying that it gives moisture and the other that it takes moisture up.
I can't find them right now (I'll try to track them down when I have more time), but a couple of the study results I've read about aloe refer to its polysaccharide content as preventing moisture loss. There are different types of polysaccharides and they are not the same things as disaccharides (like honey or agave nectar are comprised of) since they of course have a different structure and may not attract water molecules in the same way that disaccharides do.
As complex polymers, with a different structure that the disaccharides or glucoses that comprise them, I think they would be more like film-formers. I've seen the polysaccharides in aloe referred to as mucilaginous polysaccharides which seems significant to me. So since aloe juice/gel is itself 99.5% water, I've taken that to mean that rather than attract water to itself like a true humectant would do, it forms a film once dried. Since we're putting it onto hair which is naturally porous to a certain extent, my understanding is that the hair absorbs the aloe's water content and consequently that moisture is bound inside by the film that is formed as the aloe dries. Not that the aloe itself attracts moisture from other sources.
Of course, I could be totally wrong. I do wish our Curl Chemist would join in...