As it says in the caveat, the quiz uses the regions that are considered by JetPunk. JetPunk considers them as separate, as Autonomous Okrugs. The area is according to Wikipedia, which also puts them separate.
I mean even in Wikipedia (in article "Federal subjects of Russia") when all 3 are put in the table as separate then area is not double counted so Tyumen's area drops to 143,520 km².
Did I clear your doubt?
Thank you! :)
Thank you for your warning!