It came from the Bing toolbar tracking the user browsing. Yes, obviously "hiybbprqag" came from Google. But that's because they only tested it on Google.
They never tested the fact that it could have come from any other website as well. Thus, they can't conclude that Bing is copying Google or whether its copying the user's browsing behavior.
"Bing results increasingly look like an incomplete, stale version of Google results—a cheap imitation"
Which they have NOT demonstrated. Their results can easily be interpreted that they imitate user clicks.