This will be interesting to see, as I've just bought a new Golf.
Assertions here of a universal tank tapped by nearly all fuel transport are correct. There are exceptions in some cases, but it's absolutely correct that branded additives are added to the same fluid. It's essentially post processing of the refined product. Oil is a commodity, and fuel is a derivative of that commodity. It's sold by the barrel, not by the brand of the extraction entity. Exceptions tend to stick out plainly, such as the obviously higher-binned Sunoco 94 when it was around.
Doesn't mean it's better quality or better for your car. It's just different. Computers are very good at sorting this stuff out, as much as I personally like to gripe about them on occasion.
One thing I've found that may or may not make a difference on this vehicle is that oil change interval and even the oil itself (to a point) can have a larger effect that people seem to expect these days. Not a few months ago, someone pulled apart my Rover V8, which is not a direct comparison to anything in a Golf, really; but there is a tertiary data association.
A heck of a lot of people pull the valve covers no NAS Rover V8s to find things incredibly filthy; with gunk buildup everywhere. It's just plain nasty. The old Buick lumps have some "tendencies", despite their relative clean running. If they ate beans they wouldn't run you out of the room, but you wouldn't want to be a doctor with a scope up the chute... So, you can expect to find some filthy parts in there; but not in mine.
It was a twenty year gamble, costing thousands of dollars over time, but I changed that oil every 2,000 miles since the break-in; using 25,000 mile Amsoil like dollar store discount gallons in a somewhat pointless attempt to eliminate the variable of break-down. I drained it amber every time; not because the oil itself was no longer effective, but because it was picking up carbon particulates, as oil tends to do. Every second change included a flush with Mobil 1 before refilling with the "good stuff".
Yup. I did that for twenty years.
The result? It was clean. When I say clean, I mean the aluminum had only barely developed that golden tint. No junk, no nastiness... A couple of teaspoons of sludge were found in the oil pan, which had never been removed.
That engine isn't the same by a country mile, but it was interesting. I'll probably do the same with the Golf, but one thing is certain: Financially, it's not worth the headache; because I'd have to do it several more times on new Rover V8s for twenty years to even verify that was a useful result. Perhaps I was changing it twice as often as needed to achieve that result. Perhaps I just got lucky.
Regardless, the industry moves a little too fast and is clogged full of too much branding and short attention to really have a go at determining the truth of this scenario. The only way to find out for sure would be to buy several Golfs and maintain them with different fluids, driving styles, and on different schedules.
Manufacturers have an incentive to produce vehicles that exceed the duration of their warranty with minimal service, but we don't interact with manufacturers. Dealerships have no such incentive. For better or worse, preventative maintenance is good for them.
I bought the service package with my Golf, as I'll be taking it in when I'm supposed to anyway, so I might as well not have to worry about a few of the events. It will be interesting to read all the fine print and see what exactly Volkswagen requires every year in order to maintain the warranty coverage.