A quick google search brought me to the following dissertation on brewing science, which discusses beer aging: Dissertation by Michael Wurzbacher at TU Munich (Weihenstephan). It contains multiple references to the pro-oxidative nature of ascorbic acid at realistic concentrations. The thesis is in German, which the OP is supposedly rather fluent in, but many others may not be. I could try and translate individual pieces, but the only thing worse than my knowledge of chemistry is my knowledge of English terms used in the realm of chemistry.
I'm sorry, I know referencing something that almost noone can actually read is sort of a dick move, but still it seems to be a legitimate reference demonstrating that it appears to be an acknowledged fact within the brewing community that ascorbic acid doesn't work in beer.
Not a dick move--thank you for posting. Maybe a copy-pasta run through Google translate will yield a rough English translation.
This brings up an apparent contradiction. I too have seen claims of AA promoting oxidation when used by itself, most notably on that other brewing site. Yet, AA is used extensively in the food and beverage industry as an antioxidant. So, at what point do these outcomes diverge, and what is the determining factor?