That's nothing...! My friend's smart-TV asked if I wanted to login on the Youtube app, presenting me with my username, after I'd spent an evening or two showing

That's nothing...! My friend's smart-TV asked if I wanted to login on the Youtube app, presenting me with my username, after I'd spent an evening or two showing my new friend a bunch of YT vids on it (music/bands and more). My phone and tablet were indeed on the same wifi, but they're not Android. And neither are my friend's devices. Except for the TV perhaps, IDK what the OS is there, it's not Apple for sure. But I did pull up a heck of a lot of my favourite videos, for many hours. And previously the Youtube app on the smart-TV was mostly un-used. I guess it thought I might be the owner / primary user of the smart-TV. I thought it spooky. (I'm a software engineer by trade, I kinda totally understood how it might be done — but I'm also quite a privacy advocate, hence: spooky)