Why does Google Chrome allow pop-ups by default for YouTube?

Question

Google

There is an option in Google Chrome settings to "Block pop-ups on all sites"
On my site, the clickable "Share" button from Google+ does not open a pop-up window the first time. There is a message "Pop-up window blocked"
However, on the well-known video hosting site youtube.com, after performing the "Share" action on the video to the Google+ social network, a pop-up window opens.

Answer 1

Well, the answer, in principle, is obvious: who do you think owns both of these products: both the browser and youtube? :)
In fact, Google may well do whatever it wants with the browser at its discretion. Including ignore your settings. And nothing will happen to them, alas.
// by the way, for completeness of the test - it would be nice if you tried to reproduce in Chromium

Answer 2

On my site, Google+'s interactive "Share" button doesn't open the popup the first time. "Pop-up blocked" message is observed

As it turned out, pop-up windows were blocked due to a Javascript programmatic call to an interactive Google post.