There’s truth in what you’re saying, especially in the “things mostly suck, so expect that” world.

But in the ideal world you’re wrong... it’s fundamentally easier to start with a mobile design and make some specific interventions to make it work well on desktop than to do the opposite.

Whether anyone actually makes those interventions is, as you indicate, somewhat unlikely.

Yeah, but surely the vast vast majority of dropbox's business has to come from PCs. Given how hard (and wrongly) they are pushing to be a collaborative space for work documents, I think I must be correct about this. I know it's cool and all to imagine everyone working on their phones, I just can't see that as a viable work process atm.