Big kickstarters often send out physical goods as rewards. In general, the rewards on both platforms are only interesting to superfans in the first place, whether they're physical or digital. It would be impossible to measure, but I can't imagine it's that common for those exclusive rewards to be pirated, or for someone to decide not to give money because they can get the restricted content for free.

If your argument is that both theft and piracy make the "owner" of the "property" feel bad, then I don't think that really proves they're the same thing. Neither does the fact that in both cases, someone who did not create the product is profiting from it; it's not a zero-sum game, their profit isn't equal to your loss.