there's more than one way of looking at the points he's made
I thought the longest chain ultimately decided which transaction "was first".
In other words, although at a granular level it appears arbitrary in that one node may see one transaction first and another node may see the other, the aggregation of the network still acts to mitigate ambiguity using majority rule. If you introduce economic incentives at the 0-conf stage, doesn't that usurp that arbitration role that the network has ? It at least changes it. I think that's Todd's whole idea in fact.