That isn't particularly similar. The reason "Apple rejecting applications that use buttons" is a poor description is that using buttons is very, very weakly cor

That isn't particularly similar. The reason "Apple rejecting applications that use buttons" is a poor description is that using buttons is very, very weakly correlated to Apple rejecting your app. That isn't true here: If you use the Dropbox SDK, your app gets rejected. In fact, it's a causal relationship.