i have 2 friends who have EU imported cars from Germany, one is a Eurovan and the other is a golf, unfortunate neither are TDI but still.
I always ask the engine code, you never know if the PO did a swap or its an import or something. I dont want to give out bad info so i ask but everyone always rips on me for asking lol, because, well, as you stated, there all 99% to be a AHU
Yes, you will notice I said US cars, which implies that it is exactly what VW imported through normal channels, not what happened to wander in to the country via Canada or through grey market imports.
People who have cars or engines via non-normal channels will typically tell you what they have in the initial post because they know that what they have is special, otherwise it's assumed that the person with questions about their B4 Passat are working with the 1Z engine, but either way AHU and 1Z are close enough that we don't distinguish between that around here either.
To ask if a person has an ALH or AFN is unnecessary. The AAZ is really unnecessary because this is a TDI forum and not just diesel in general. The Vortex diesel forum covers all VW diesel cars and several members field questions there as well.
And actually asking this question about different engines can confuse people who are not so familiar with the TDI cars.
The people you mentioned who've imported cars know what they have and know about those vehicles, regardless of whether they're tdi or not. They are familiar with VW's and obviously wanted something specific so they imported through non-traditional channels. The casual or newbie B4 or Mk3 TDI owner who posts up looking for help is not the person who's importing a particular VW from the EU. The latter would preface their conversation with the engine info up front because they would know that their imported car is an outlier in the US.
I'm surprised that someone actually bothered to import a Eurovan or Golf to the US. There must have been something very special about those to warrant the exorbitant costs and hassle associated with importation, especially since VW brought both those to the US via normal channels during the 1990's.
Steve