The core focus of early crypto was decentralization, not anonymity. Bitcoin is totally decentralized, but the entire premise is the blockchain contains a permanent irrefutable ledger of transactions. Basically everyone knows if Wallet A paid Wallet B. If you refill your wallet with anything remotely traceable, that means everyone knows YOU paid Wallet B, and similarly if wallet B has any ties to the real world, the lines are easy to connect.
That’s not to say you can’t use it anonymously, but that was not the intent and thus it does anonymity poorly.
This is an ego fluffer app, not a scientific study. The accuracy is “good enough” to give you a rough idea of your performance, and if youre really into optimizing WPM, give you a way to track progress or the impacts of using different keyboards.
Getting a high score doesn’t actually mean anything except you probably use your phone too much.