The "contaminants" are in the filter media, and the old oil which gets drained out as soon as you remove the filter, which is why you are supposed to loosen, but not remove, the upside down filters FIRST, and let the old oil drain down into the engine where it gets drained with the rest of it. It works well, not sure exactly what you are asking about here.
I mean, really any version works fine, just that the upside down cartridges make the least mess and the least waste.
The bottom side cartridge filters are the same for waste, but they require a drain in the bottom of them in order to minimize mess.... but in some cases (like the BWT engine in an Audi A4, for instance) you still make a mess. The 2015 TDI engines also seem to require some care to not make any mess. But an ALH or a BEW or a BRM or any of the new 1.8L (CXBA, etc.), you do not make any mess whatsoever. Same for the newer VAG V6s.
Also, regarding the bottom drains, often someone mucks these up if they are an Allen plug (like many of the older VR6 engines and a lot of Ford/Mazdas). Plus, while the engine's drain plug may be right out in the open, the filter underneath may not be, and require some extra steps to gain access.
The oldest versions of this type of filter I can think of is MB...their diesels and V8s had these before I was born. They work great. And those engines' longevity is legendary.
In the case of the 1.4L VAG engine (the topic of this thread), the engine lubrication system design and intake plumbing really would not easily allow for a top side cartridge filter, but they *could* make a small housing that attaches down low to the front of the block (like the VR6 engines) with a bottom side cartridge that would be right out in the open too. But as it is, at least the spin on can is down low, with really nothing under it, and it screws directly into the front of the engine. Just no way to drain it prior to taking it loose, aside from punching a hole in the side of the can, which really doesn't drain it all anyway (I've tried).