No, it happens when you load the page. As a test I made a simple web page that just said "This is a test" and included the Google embed and visited it in an incognito window in Chrome and looked at what happened in the inspector. I used an incognito window to ensure that I wasn't starting with any cookies already saved for Google.
Just displaying the page with the embed hits those sites. All in all there were around 20 successful network requests made to load the site. There were another 7 or so requests the Ublock Origin blocked, to play.google.com/log, and then after the page loaded it continues trying those every second or so, although it seems to have slowed down after around 19 but is still ongoing.
It leaves 5 cookies (4 persistent, 1 session) and also looks like it has something in IndexedDB.
Similar with Firefox in a private window except it stores one fewer persistent cookies.
On Safari in a private window it has similar network access, but no cookies.
Just displaying the page with the embed hits those sites. All in all there were around 20 successful network requests made to load the site. There were another 7 or so requests the Ublock Origin blocked, to play.google.com/log, and then after the page loaded it continues trying those every second or so, although it seems to have slowed down after around 19 but is still ongoing.
It leaves 5 cookies (4 persistent, 1 session) and also looks like it has something in IndexedDB.
Similar with Firefox in a private window except it stores one fewer persistent cookies.
On Safari in a private window it has similar network access, but no cookies.