The point is, everyone trusts the genesis block, and all updates from there are made via pow. This is essentially a proposal for a consensus process to update the genesis block forward, and to attach a tree of utxos so that the txs between the new gen block and the old never need to be seen again (we can put them in a museum of bitcoin history, if you like, but spare the new full nodes!). I still have not heard a reasonable argument as to why this can't/won't work.