I love the idea of this, but recently (2/2020) it hasn't been working. Facebook still loads in the container, with a white bar underneath. But it is definitely still seeing my search history in other containers. I'm getting ads about quitting smoking.
I have never smoked. But yesterday I did a lot of research on rehabilitation from drug misuse for a character in my novel. This is the only time I can think of that I even approached the topic of drugs or addiction on my computer. But facebook knows, despite being in a container. :(