Wikipedia disagrees with you. While it doesn't say if there is any of it in nature it says it's normally produced by via hydrolysis of starch, not simply extracted.
Hydrolysis of starch is a completely natural process. It happens all the time in nature.
Reproducing that process in vitrio doesn't generate a different end-product to the in vivo operation of the exact same process.
That's the whole problem with 'natural' food - even if you can define what it means, it is meaningless as a means to differentiate between two end products. Refusing to eat food that's not 'natural' is as sensible as refusing to drink water that was generated by burning Hydrogen, rather than distilling it from sea water.
The job of the FDA is to ensure that consumers know when two products are materially different, in ways that could affect the people who consume them. Labels such as 'natural', 'organic' or 'non-GMO' do NOT achieve that objective, and should simply not be used at all.
Moreover, combining ingredients and adding heat or pressure to create things that don't occur in nature is called "cooking".
Maltodextrin created, as you term it, in vitrio takes naturally occurring things and by following a recipe cooks up something new.