Romneyland says attacks on his offshore tax havens 'proven false.' But where's the tax return proof?

In the wake of the new Vanity Fair article raising questions about Mitt Romney's use of offshore tax havens, Romney campaign spokeswoman Andrea Saul responds to criticism from the Obama campaign and Priorities USA about his financial secrecy:

President Obama's attacks on Mitt Romney have been proven false time and again. As job growth slows, manufacturing activity stalls, and our economy continues to sputter, President Obama knows he can't make a legitimate argument for another term in office, so instead he is trying to tear down his opponent. This is just the latest example of President Obama and his political machine saying or doing anything to distract from his abysmal record over the last four years.

Proven false? By who? And, given that Mitt Romney still refuses to release his tax returns before 2010, by what? Everything else in that statement is misdirection. There's a reason Mitt Romney isn't releasing those tax returns, and until he does there's no way his campaign can make the claim that concerns about what may lurk in those documents have been "proven false." They haven't.