GWM, yes it does take you by surprise when you find it.
It is a very peculiar way Vaude has for shortening the length of the poncho.
If you look at the hem, as well as the press studs for fastening front to back between your legs to stop the poncho blowing up, there are two further straps with a few press stud fasteners, without looking I think two on each. So if you want the poncho to be shorter you attach the chest tape to the hem tape, front or back, maybe even both? You can then also still have enough press studs to fasten the poncho between the legs.
Now having written all that, Since I am well over 6 got tall, I never needed to experiment with it until today.
I think personally that this is yet another thing Vaude got wrong with that poncho.
To me the only thing that is right it's total waterproofness and airyness and I like the between leg tie down.
I find it just too heavy for carrying on my daysack on the off chance of rain. The rucksack pouch, adjustable to the size of rucksack, is like carrying an elephants hernia. Their sizing is on the ridiculously large side of large. I ordered an L, the label says L but my body tells me it got loads of kisses in the making as it feels more like a 5XL. I have a decent waterproof jacket but still would prefer a decent poncho. I am sure that the Decathlon zip up or the Altus meets my requirements. Failing that I may go down your current Champion route.
As for the Vaude well I see a ground sheet and some dry bags coming out of that.