In German they are called Doppeldecker which means double decker (what a surprise). So maybe they were just translating things a bit too quickly.
@ Xabba
No, if that had been me the entire area would have gone up in flames.
I guess he spinned a few times more than he wanted and couldn't pull her up in time after that. It's a relief that no one died.
We have already had deadly accidents while doing aerobatics at our airfield. I really hope that such a thing never happens when I'm around.
BTW that's also the reason why aerobatics mustn't be performed over the audience in Germany.