Anyone know for a fact, who makes the VW brand G055540A2 fluid?
No particular company makes any of the GXXX fluids. Any GXXX is just a set of tolerances that the fluid has to meet in order to provide a proper lubrication and not harm any components. Then VW tries to source it from whoever can provide a fluid that meets all the specified tolerances. But it can have several sources depending on geographical locations (ie. VW will not ship it all the way to the US or to Australia from Europe, unless it absolutely has to, because no American/Australian company can provide it), and the actual suppliers can change over time.
So, when for ex. a European Touareg owner buys genuine G 055 540 A2 from VWoA, he will not actually get the same fluid than what an American Touareg owner gets from VW Europe when he buys G 055 540 A2. Or if you bought G 055 540 A2 from VWoA in 2015 that was possibly supplied by a different oil company than who made the G 055 540 A2 that VWoA will sell to you now in this very moment. But of course they all met and meet the G 055 540 A2 tolerances - and in the end that's all what matters.
So, as long as the oil company claims that a particular fluid it offers "meet or exceeds" a particular OEM spec, and you trust that supplier, you're good to go with that fluid. If you're super OCD, then look at the actual bottle of the OEM fluid (which, again, might change depending on region or over time, for the reasons explained above), and try to look for an oil supplier which sells its product that "meets ot exceed" said spec in the very same or at least in a very similar bottle. Then if you buy their stuff, you will be actually buying the very same fluid that also VW sells to you, just with a hefty surcharge and a different sticker on the front and back of the bottle.
In the case of G 055 540 A2 it's Febi Bilstein that offers a fluid (29934) that meets said spec and comes in a bottle with the very same shape as the OEM fluid. Guess why?
PS: The most reputable manufacturers will not only say their fluid meets a particular GXXX spec, but they will actually mention the cars and transmissions their particular fluid is intended for and has been tested with. For ex. Ravenol also has a G 055 540 A2 fluid (T-WS Lifetime), but they not only say that their fluid meets said spec, but actually explicitly mention on the bottle that it's intended for use and has been actually tested in 0C8 transmissions of Touaregs made after 2011 and in Q7s made after 2010.