No, it's a joke sentence, they are just trying to be funny. I think it's all very well and good that they try to make things humourous but they just confused people with this one because onions are a food item and can be revolting to some, either because they are badly cooked or the person just hates onions. It would have been better if they had used a different noun, something people don't eat. Just my opinion. Back to my cave!
The problem with silly sentences like this is that they can be confusing and lead to us being marked down. In this instance, I typed 'De oudjes kwamen in opstand', which I think was pretty well justified, and the pronunciation is not that different (if at all). As a result, Duolingo will have put me down as needing more practice in this section.
Crazy/ fun/ silly sentences are fine, but contributors should bear in mind that learners at an elementary-intermediate level rely heavily on context when trying to figure out the meaning of an unknown word or phrase, therefore such sentences can be very confusing and counterproductive.