I don't think he sandbagged in Q2... He nearly dropped out there!
Actually, wrong logic on Button's speed. He's fast and smooth, but a single flowing move is the slower way of completing a corner. View it this way: Every square centimetre of tarmac has slightly different grip-levels. Every bit of the tyre grips slightly differently. The best way through a corner is keeping it on that very limit on every given moment - in order to keep the car smooth and on the optimal trajectory. That involves twitching and changing the steering-angle constantly in order to adapt for the changes. If you watch the really fast onboards (yes, even Jenson's classic TC-aided 2004 Imola lap), you'll see constant corrections to the wheel on anything grip-limited rather than power-limited.
There's a pretty little anecdote regarding a Porsche Supercup race at Spa. Two onboards were shown - one of a smooth driver doing everything in a single, flowing, and one showing a driver hectically adjusting steering-angle, and constantly adjusting his throttle and brake-input. The outside shots showed something else - Mr. Smooth was, well, smooth, yet the other driver's car seemed calm and controlled as well. One of them, however, was three seconds faster on that lap - I'll let you guess who.
It's a setup-, track- and style-issue, on top of that. Look at Alonso's infamous early turn-ins in the Michelin Renaults - these don't work on the Bridgestone tyre and yet, on these Renault, on these Michelins, were the fastest way to get it around the track.