I speak (Austrian) German and it sounds a lot more like a German dialect than Dutch to me (there are so many of them, though, this is not really saying an awful lot). Like the Dutch speakers who've chimed in, I don't understand much of it but can pick out enough words to tell where the other, incomprehensible words are.
Having listened to the above youtube video, I think resemblance to allemanic might be coincidental, as it is so often.
Judging from the pronunciation, I would also put some "idioms" of this dialect in Dutch/Flemish regions (there is maybe a distinct polish influence in there that throws one off?).
As so often for me, the written word it seems is way more understandable than the spoken word. I had the same experience with Swedish. Weird how some languages kept similarities in writing longer than similar pronunciation.
There are also a lot of strange tricks personal perception and familiarity play on you. I found this easier to listen to first and then listen and look at the text together later. I similarly find myself thrown for a loop whenever I see Viennese/Bavarian written. 'Wir sind' - easy to read and hear, 'mia san' easily matches up with the former when heard. 'Mia san' written down and for a moment I have no idea what I'm looking at. Feels weird to even type it out.
German influence. Before ~1918 area was a part of German language 'island' of Bielitz. A town nearby called Hałcnów had a similar local language that was much more similar to German.
