In the past, I have bought acacia gum from exotic nutrition and as far as I can tell, they do use the Australian sourced gum since the powder is darker with what I would assume are tannins. As far as I know, all gum is going to have an ash content which is basically where all the minerals like calcium and magnesium are going to be found when doing an analysis, I'm not sure that its from processing.
I've bought the african species gum powder and it is typically off white with very low tannin. The African species gum is much cheaper and fundamentally the same thing as the Australian stuff except for tannins, which for the most part aren't likely to be all that beneficial and in my opinion are dispensable.
Yes, I would be skeptical of anything processed in China. There are places in the US that you can buy certified organic, safely processed(not from China unless I've been lied to) acacia gum powder that I have safely fed my gliders for years. You can buy the powder and mix in juices, water or pollen at your house. You can make your own gummy treats without having to pay a bunch of money to someone else to ship you a rehydrated product
Gliders have a modified digestive system that incorporates an enlarged caecum that definitely makes use of some microbial fermentation to break down the complex polysaccharide linkages in the gum. I don't know if 90% is a valid figure or not though. It seems pretty high. Either they are doing some researching/experimenting, or some good story writing.