The "wave of consensus" refers to the fact that a decentralized network cannot have a definition of "current state" for everyone in the network. There's some so

The "wave of consensus" refers to the fact that a decentralized network cannot have a definition of "current state" for everyone in the network. There's some sort of "undisputed state" because as blocks pile up, it becomes more and more impossible to alter the older blocks and also generate the amount of blocks required to overtake the original chain. That's the wave: new blocks propagate on the network, ensuring the older blocks can't ever change, but the newer blocks might be replaced by others in some cases. This is why there's a need to "wait for confirmations" in most crypto transactions.