Google launched a news-reading app called Currents on Thursday, something it has been working on for some time — ever since it was a much-rumored skunkworks project called Propeller — and much of the coverage of the new app has called it a challenger to existing tablet and iPhone news-readers like Flipboard and Zite. But while Google Currents is superficially similar to these other services, there are some important differences that make me wonder whether Google really understands how media has changed and is changing. For a company that’s usually so forward-thinking, Currents as it stands now is more than a little disappointing.