VAG has several filter suppliers. Mann, Mahle, Purflux, Hengst, UFI, etc.
It varies from engine to engine, and the same engine type may have several different ones. Most ALH engines use a Mahle or Mann+Hummel oil filter assembly.
You can find out which one by looking at the side of the aluminum casting. Mahle's symbol is a little square with a fat arrow with sguiggly lines in it. It will have the Mahle brand filter element number right next to that, OX143, along with the VAG element number.
The Mann+Hummel ones will say "MANN+HUMMEL" on them, in a similar location, and their symbol which almost looks like a heart in a square with a big block line through it (I think it is actually a stylized "M") with the Mann filter element number HU726/2x along with the VAG element number. Usually the Mann supplied units also have their name on the cap, too.
Most ALHs have a Mahle assembly. However, both elements will fit and work perfectly fine in either housing.
All the ALHs have a Mann air filter housing, and they have the appropriate numbers on them as well.
BRMs, on the other hand, use either Mann+Hummel oil filter assemblies or Purflux. They are also marked. They also always use a Mann air filter. BRMs also use Mann fuel filters. ALHs, BEWs, and BHWs all use Bosch fuel filters from the factory.
The only thing I know fro sure that Hengst supplies VAG is the 2.5L 5 cyl gasser valve covers, the EA888 2.0L gas turbo crankcase pressure regulator valves, and some other gasser items here and there.
Lots of times, the aftermarket retailers label ANY of a particular brand as "OEM" to a manufacturer, even if that particular part was not actually used as the original equipment. So you may look up a spark plug for a Toyota, and see Bosch listed as "OEM", when in fact, no Toyota anywhere ever used a Bosch spark plug from the factory... they are almost always Denso with a few NGKs, but never ever Bosch. But, since Bosch did supply Toyota with some ABS units in US-assembled cars (Camry), they get to where the "OEM" badge. So you really have to often read between the lines to know what you are getting.
But if you really want the "best" filter for your TDI, find out whose housing is on the engine. We use Mann oil filters almost exclusively here on all VAG applications, as well as BMW, MB, and others, and have never had any issues with them. They seem to work perfectly fine even in housings made by Mahle or Purflux.
Oh, and Purlfux' symbol is just a square with wavy lines in it, similar to Mahle's but no arrow. Again they usually have their name somewhere on the item as well.
The last of the original Volkswagen died off shortly after Heinrich Nordhoff. The last hoorah being the 411, which, among many other firsts for Volkswagen, DID have a conventional spin on can oil filter on its all new engine.