On firefox it is an option to “clear data”. It is separate from the history. You want to clear both.
“Cache” is where these both are stored in the files. So techs use the term “clearing the cache” in reference to clearing both of these out to have an empty cache.
I did clear both data and history, as I recall. What a mess.
You’ve clearly explained the how of what’s going on. What I’d like to know is why? Either Alphabet/Google/Youtube is collaborating with the government to gather our info, or the corporate scum want something to hold over the “customers”, or they’re doing something that makes no real sense at all.