Whincup didn't just randomly jump on the brakes. This is, after all, a professional motor race, not a GT6 online lobby. So yes, he did have a reason for doing what he did; it just wasn't a very good one.
You are correct in saying that Whincup could have redressed further down the road. But he was clearly trying to redress the position to McLaughlin without losing position to Tander. Had the move worked, McLaughlin would have rejoined the circuit ahead of Whincup, who would have been ahead of Tander. The problem was that Whincup had no right to be going that slowly. His move on McLaughlin was messy, and the redress was a suitable penalty. If redressing meant yielding a place to Tander, then Whincup should have taken his lumps and yielded. He had the pace to re-take the position anyway.