He's creating confusion by treating front ends or clients like (Metamask, Opensea, and Infura) as servers when they are actually clients.

So dapp -> infura -> blockchain is really client -> client -> blockchain.

When multichain interoperability becomes widely available (See polkadot, cosmos, etc) blockchains will also become clients as well. Clients at any level won't be bounded like they currently exist in centralized networks.