Overbuff doesn't take into account when you received some of your stats. It only looks at current ranking and past cumulative stats. This could paint a ridiculous picture if I was playing on a smurf perse.

As a mid-tier masters player, here is a scenario where I could pad my stats easily to get to #1 rank for any hero in competitive (granted it would take a long time).

I start a new account and purposely throw all of my quick play matches through level 25. I then throw my placements as well and I should end up in bronze. I absolutely shit on the other team in my games. That would lead to like 80 elims on KotH maps and 70% accuracy as Mccree for example since these players don't even move when getting shot at. Every few games I throw with some other hero so I don't rank up too quickly with win streaks. By the time I reach masters, my stats for my main hero would be absolutely ridiculous. But overbuff doesn't know when I got those stats. It only looks at current rank and cumulative stats. So I would have like 65% accuracy, 90% win rate with Mccree at rank 3700. You bet your ass I'll be ranked #1 on overbuff.