ALH exhaust valves (part number 028-109-611-G) are 96.85mm long.
BRM exhaust valves (part number 038-109-611-G) are only 89mm long.
That is why the BRMs have shorter valve guides. They have shorter valves.
However, you can use the more widely available longer guides in the BRMs, but some folks will chuck them up in a lathe and machine them shorter to match up with the originals.
Since VAG does not sell these apart from the head we are only able to get the aftermarket stuff, which are technically from a gasser (hence the 037 prefix part number) which VAG does sell by themselves. And in ETKA, that guide only shows up with various gas engine cylinder heads, but never with the diesels. Because it is not the same guide the diesels' heads left the factory with. It is not an "update", we are just using the wrong-but-available-and-usable gasoline engine guides in our diesels.