Highlights

Almost all dApps use either Infura or Alchemy in order to interact with the blockchain. In fact, even when you connect a wallet like MetaMask to a dApp, and the dApp interacts with the blockchain via your wallet, MetaMask is just making calls to Infura!
t reuses the same connections, TLS session tickets, etc for all the accounts in your wallet, so if you’re managing multiple accounts in your wallet to maintain some identity separation, these companies know they’re linked.