They could of course be sharing the click "back channel" with the ad network without any visible redirect at all, and still capturing just as much data. I guess

They could of course be sharing the click "back channel" with the ad network without any visible redirect at all, and still capturing just as much data. I guess it couldn't actually set a cookie with the viglink.com domain though. Is that important enough to risk being "found out", or do they just not care that much about being found out, so went with the somewhat technically easier to implement but visible to end-user option?