The Recode article in December touched an important point about the name "Clear History" [0]

> There’s a reason that Clear History isn’t called “Delete History”: Using the feature will disassociate browsing data that Facebook collects from your specific account but it won’t be erased from Facebook’s servers completely, Baser said. Instead it’s just “de-identified,” which means it’s stored by Facebook but no longer tied to the user who created it.

[0] https://www.recode.net/2018/12/17/18140062/facebook-clear-hi...