Sandboxes or containers are a great idea, but really there is always going to be some sort of idea of what browser is visiting a site. This post was not focused on hardening a privacy workflow as much as it was taking one egg out of the basket to prevent misunderstanding and provide another measure of security. As far as tracking across domains goes, sandboxing is a great tool, as is keeping an updated list of trackers not only in-browser but in your Operating systems host file as well. I recommend the following sources to get started hardening an OS and catching domains and elements that are not filtered by privacy extensions:
https://github.com/hectorm/hblock