This works beautifully as intended.

One disadvantage compared to the regular portafilter is that there is one spout. This is obviously the whole point of the portafilter, but let me explain: when trying to level the coffee, or tampering it, you cannot rest the portafilter on that one spout. If I were to introduce a small design change, it would be an extra leg, the same height as the spout, so it can rest on two legs.

Or maybe we've been doing it wrong all along.