All of Chris Dixon's tweets you embedded in your Medium post are correct.
Data stored on the Ethereum blockchain and similar ones is public and anyone can build against that data. This is due to the fact that the blockchain is a shared public database. If Twitter's account and tweet data were on-chain, anybody would be able to create a Twitter client that surfaced the social graph and related data in whatever UI they chose and Twitter could not stop it.
If you're technically minded, try building a few throwaway Twitter projects on Ethereum testnet (or Solana, or Avalanche, etc) and get a feel for how it works!