Translation:How long does the competition continue?
The alternative translation "How long does the competition continue?" I find unnatural, but the other option of "How long does the competition last?" is something I would probably say.
And yeah, I'm pretty sure that's what it's trying to convey.
(probably you don't need this commented on now but heyho)
Sometimes I think it is just because the Eo sentences themselves are a bit awkward, for teaching purposes, so the translation comes out similarly so.
For all other cases, I wonder if it might have something to do with the course creators wanting to be more lenient for people taking the course without a strong grasp on English. After all, this was the only course on Duo teaching Eo for a while (there's also now Eo for Spanish [in beta] too).