That's why great care is taken that they
don't see it. How often do you, on Facebook or Twitter, see "This message has been censored/had its visibility limited due to [reasons]"?
They put up fact-checks under a post sometimes, but what those fact-checks mean for the visibility of a post is left to your imagination. If a post or link is outright censored, you don't find out about it until you try to post it. As their censorship intruded even into so-called private messages on those platforms, even in a 1-to-1 conversation, sending something prohibited doesn't show any kind of "Prohibited content censored" message to the recipient (even non-spam).
They'd much rather you don't know they're censoring anything.