I did some testing. I have 2 Google accounts, and what I found was that on my main account (which I use with Chrome), Google knows my computer name. On another account, I am logged in with Edge and Firefox, but neither of them show my computer name. It was not until I logged into the Chrome browser ITSELF (not the Google page) as a Chrome user that my second Google account showed the browser I was using.
I verified this on my laptop: I logged in with my second account into the Google website on a new user, which didn’t update the computer name on either device in the security settings. Once I logged into the Google Browser with that account, it showed my computer name. So it looks like because you’re logged into Google Chrome, Google knows your computer name.
Note that Google using a sandbox does not make any difference for this. It is trivial to find your computer name, all it takes is hostname in a command prompt.