Honey and agave syrup have oligosaccharides that act as stabilizers. Fructans in agave, specifically.
As does molasses like when making refined sugar. Most unrefined sources of sugar naturally contain chemicals that act as stabilizers because it’s a side effect of many polysaccharides.
Right, but honey and agave syrup can also act as mild adhesives. I'm not sure anyone would consider them an adhesive any more than they would a stabilizer.
Also "Greek yogurt" is normally strained so it's already stabilised and is less subject to syneresis.
Note that even with the stabilising effect of straining and honey, real Greek yogurt (the stuff without additives) is never sold with admixtures. Once you mix stuff in you really are changing the consistency of the product and therefore its storage and transportation profile.
There's a scene in Silicon Valley [1] where Elrich Bachman is complaining that people keep taking his narrow spoons that he needs to mix in the jam in the little tub attached to his "Fa-Yeeh yogurt" (spelled "Fage". Surprisingly he pronounces it right! I'm Greek).
Bachman is talking about this product, Fage's split-cup Total yogurts:
https://gr.fage/total-2-split-cup
The reason there's a little tub and you have to tip it in and mix it up after you buy it is exactly because once you've disturbed the yogurt by mixing things in it, you don't have yogurt anymore but a gloopy goo with the consistency of thick cream and that just doesn't travel very well, especially if you want to be exporting your yogurt from Greece (where Fage has its plants) to the US (where Bachman complains about his spoons).
Also that gooey gloop is not what yogurt is supposed to be like. But I suppose that's just a matter of habit.
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