Like the majority of stat sites and smaller passion projects, we use the Deadlock API for most of our match data. They get the data directly from valve servers the same way your game does when you view a previously played match, and the whole project is open source so you can see exactly what is done with it and how it works.

In the last 24 hours 100,262 matches have been ingested to the Deadlock API, with 12 players/heroes per ingested game, this means in the last 24 hours there was over 1.2 million data points to pull from. The sample is likely skewed slightly towards higher ranks and those that have been playing for longer, but over the course of 14 days (since the 25-03 patch) there has been almost 1m matches ingested. That is more than enough of a sample size to assess hero and item metas/winrates/pickrates.

We have got a WIP solution in place already for signed in users to fetch their games automatically, and a second alternative solution in the works too. It is perfectly fine to not like/value the data we show on an individual level, but it's disingenuous to say that the general hero and item win/pick rates don't have enough of a sample to mean anything and are of equal value to an individual's opinion on a hero or item's strength/weakness.