> In the eyes of many consumers they’re unrelated because they’ve up until now pushed very separate branding.

I mean we are both speculating here unless there is some data to prove our claims, but I would say that Google dropped any attempt at keeping the brands too separate when they introduced the Google+ comment section.

The "Google preferred" also makes sense because all advertising that happens on Youtube is under the Google AdWords brand. There is no Youtube Ads, only Google Adwords for video.

I don't think so. The advertising business is all named under Google, e.g. Google AdWords and Google AdSense. Even the YouTube-specific TrueView ads fall under AdWords.