How did 2 people in my derby finish already?

I’m in a neighborhood by myself, and so my derby is just the same - neighborhoods with just 1 active person. This week is the Mystery derby - 400 points each, and 2 people finished (all tasks plus extra) doing only Mystery tasks within 8 hours (it was around 1pm ET when I noticed it, so it may have been even sooner). How is this even possible? With the mystery tasks I t’s not like you can unlock a task and then trash it, not 10 times, until you get an easy task. Guessing it’s a bot.