If they struggle with first stage re-usability for a while, that merely adds cost. Further they probably want to iterate and scale anyways, so in the short term

If they struggle with first stage re-usability for a while, that merely adds cost. Further they probably want to iterate and scale anyways, so in the short term they're gonna be building a lot of first stages anyways. Second stage reentry is necessary for this thing to ever carry people, ostensibly the mission the ship was designed for. It is a hard requirement.