If you want to test for yourself. Go to bing chat and write a message and asks for the question. When the bot starts writing, switch to some other tab and wait a few seconds, than go back to the previous tab and you will see that the message had stopped during the time you left the tab. I tried to search about this, but aside some post on the ublock subreddit (https://old.reddit.com/r/uBlockOrigin/comments/185j3gg/help_block_visibility_api_for_bing_chat/), I couldn't find any explanation.
I was just curious and wondering if anyone on HK has any idea why/how they are monitoring when I switch tabs?