I sort of hoped for Horizon to be a launch title. But in the end it does not matter too much.
Sony (or Microsoft) do not really need a great first party line-up. There is a group of people, millions strong, that will buy the console no matter what. I even read a while back, that PS5 might end up a bit supply contrained.
Sooner more exlusives is better, sure. But it might be good strategy to hold some first party titles back until all the hard core people have bought a PS5 and the potential customers that are left are the ones that need cinvincing.