Earlier quoted context omitted.
YouTube is owned by Google.
Even so. It’s a strange use of branding. It would be like Beats having a line of “Apple Preferred” headphones. 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.